Perfect numbers | Integer sequences

Hemiperfect number

In number theory, a hemiperfect number is a positive integer with a half-integer abundancy index. In other words, σ(n)/n = k/2 for an odd integer k, where σ(n) is the divisor function, the sum of all positive divisors of n. The first few hemiperfect numbers are: 2, 24, 4320, 4680, 26208, 8910720, 17428320, 20427264, 91963648, 197064960, ... (sequence in the OEIS) (Wikipedia).

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#MegaFavNumbers my MegaFavNumber is 16777216

#MegaFavNumbers I just love the 8^8 and don’t know why! :) Help us to legalise hemp in Germany 🇩🇪: https://hanfverband.de/finanziell-unterstuetzen

From playlist MegaFavNumbers

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Conversion Arcs and 2,916,485,648,612,232,232,816 (MegaFavNumbers)

I'm sorry. The MegaFavNumbers playlist: https://www.youtube.com/playlist?list=PLar4u0v66vIodqt3KSZPsYyuULD5meoAo

From playlist MegaFavNumbers

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My #MegaFavNumber is 79,873,884

My #MegaFavNumber is 79,873,884 which is the first number over 1 million that is in its own location in the digits of pi

From playlist MegaFavNumbers

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MegaFavNumbers: RSA-2048

My own choice for a number over 1,000,000 is this 617 digit boy: 251959084756578934940271832400483985714292821262040320277771378360436620207075955562640185258807844069182906412495150821892985591491761845028084891200728449926873928072877767359714183472702618963750149718246911650776133798590

From playlist MegaFavNumbers

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1,010,010,101,000,011 - #MegaFavNumbers

This is my submission to the #megafavnumbers project. My number is 1010010101000011, which is prime in bases 2, 3, 4, 5, 6 and 10. I've open-sourced my code: https://bitbucket.org/Bip901/multibase-primes Clarification: by "ignoring 1" I mean ignoring base 1, since this number cannot be fo

From playlist MegaFavNumbers

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#MegaFavNumbers - 7,588,043,387,109,376 by Egi

87,109,376^2=7,588,043,387,109,376. The last 8 digits is the square root😀, it's called an automorphic number which n^2 ends with n

From playlist MegaFavNumbers

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MegaFavNumbers - A number with 19729 digits

This video is about my MegaFavNumber. It has 19729 digits, and it is a power of two. [This link is now broken, and I can't find it anywhere else. :( ] See all the digits here: https://sites.google.com/site/largenumbers/home/appendix/a/numbers/265536 The OEIS sequence I mentioned: https:/

From playlist MegaFavNumbers

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Ex: Determine a Number that is Less Than and Greater than Using a Specific Place Value

This video provides examples of how to find a number that is less than and greater than a given number using a specific place value. Search Video Library at http://www.mathispower4u.wordpress.com

From playlist Whole Numbers: Place Value and Writing Numbers

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How is i equal to square root of -1?

What is 'i'? More importantly, what is a complex number? How are complex numbers relevant to the context of other familiar numbers? Chapters: 00:00 Introduction 01:46 Logo of Reals and Rationals 02:11 Expanding real numbers 03:25 Motivation using whole (natural) numbers 06:08 Planar numb

From playlist Summer of Math Exposition 2 videos

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Fun with Math: Surprises with Arithmetic and Numbers

Stephen Wolfram shows kids and adults some fun unique things you can do with math. All demonstrations powered by the Wolfram Language. Originally livestreamed at: https://twitch.tv/stephen_wolfram Follow us on our official social media channels: Twitter: https://twitter.com/WolframRese

From playlist Stephen Wolfram Livestreams

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How to understand the REAL NUMBER LINE - COLLEGE ALGEBRA

In this video we talk about natural numbers, whole numbers, integers, rational numbers, irrational numbers, and real numbers. We also show the real number line and the inequalities less than and greater than. 00:00 Intro 00:29 Number system 04:53 Visual representation of numbers 07:37 Rea

From playlist College Algebra

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Real Numbers

This video provides a basic introduction into real numbers. It explains how to distinguish them from imaginary numbers. It also discusses the difference between rational and irrational numbers as well as integers, natural numbers, and whole numbers. Examples include repeating and non-re

From playlist New Algebra Playlist

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What are Isotopes?

This chemistry video tutorial answers the question - what are isotopes? Isotopes are substances that are composed of the same element but consist of different mass numbers and number of neutrons. They share the same atomic number and therefore the same number of protons. This video cont

From playlist New AP & General Chemistry Video Playlist

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Pascal's wager and real numbers

My entry for 3blue1brown's contest, talking about Pascal's wager and how it leads to interesting questions about (hyper)real numbers. A big shoutout to Grant for coming up with this wonderful idea. Link to Thierry Platinis channel for more on hyperreal numbers: https://www.youtube.com/cha

From playlist Summer of Math Exposition Youtube Videos

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Year 13/A2 Pure Chapter 0.1 (Subsets of Real Numbers, Representatives and Proof)

Welcome to the first video for year 13 (A2) Pure Mathematics! This video is part of a series of three that I've called Chapter 0, and is meant as a foundation for Year 13. The primary reasons for doing this are that the difficulty of Year 13 is markedly harder than Year 12 content, and al

From playlist Year 13/A2 Pure Mathematics

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My favorite proof of the n choose k formula!

The binomial coefficient shows up in a lot of places, so the formula for n choose k is very important. In this video we give a cool combinatorial explanation of that formula! Challenge Problems playlist: https://www.youtube.com/playlist?list=PLug5ZIRrShJGkzGsXMYQt8bi5ImYtiEMM Subscribe t

From playlist Challenge Problems

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Is the Sieve of Eratosthenese past its prime?

The Sieve of Eratosthenes is an amazing tool for teaching people about prime numbers and composite numbers but it's not without its limitations. I've tried to answer the question, 'Is there a better way of representing a sieve like this?' 0:00 Sieve of Eratosthenes In the first part of t

From playlist Summer of Math Exposition Youtube Videos

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Statistics: Ch 8 Combinations and Permutations (2 of 22) What 's the Difference?

Visit http://ilectureonline.com for more math and science lectures! To donate: http://www.ilectureonline.com/donate https://www.patreon.com/user?u=3236071 We will see an example of the difference between combinations and permutations from 5 numbers (pick any 3). Previous video in this s

From playlist STATISTICS CH 8 COMBINATIONS AND PERMUTATIONS

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ALGEBRA & PRE-ALGEBRA REVIEW: Ch 1 (15 of 53) What Are Number Sets?

Visit http://ilectureonline.com for more math and science lectures! In this video I will explain what are counting numbers, whole numbers, integers, rational and irrational numbers, real numbers, and imaginary numbers. Next video in this series can be seen at: https://youtu.be/frXUlpNq4W

From playlist Michel van Biezen: MATH TO KNOW BEFORE HIGH SCHOOL

Related pages

Perfect number | Semiperfect number | Multiply perfect number | Divisor | Number theory | Divisor function