User:Charles R Greathouse IV

Editor-in-Chief, interested primarily in computational number theory and allied fields.

I can be contacted via my Talk page here, or by email.

User:Charles R Greathouse IV/Averages	Early draft of an article.
User:Charles R Greathouse IV/Chase sequences	'Chase sequences': Axxxxxx refers to Ayyyyyy, which refers to Azzzzzz...
User:Charles R Greathouse IV/Favorites	Some of my favorite sequences.
User:Charles R Greathouse IV/Format	Discusses the correct format of b-files and how to repair ill-formatted b-files.
User:Charles R Greathouse IV/Junk	Disreputable publishers, journals, etc.
User:Charles R Greathouse IV/Keywords	Information on keywords: when to use them, new ones to add, etc.
User:Charles R Greathouse IV/Metadata	Plans for OEIS metadata: keywords, categories, the index, etc.
User:Charles R Greathouse IV/Pari	Some PARI/GP tools.
User:Charles R Greathouse IV/Programs	Programs in the OEIS: types, format, etc.
User:Charles R Greathouse IV/Projects	Other mathematical databases, fingerprint databases, and similar projects
User:Charles R Greathouse IV/Properties	Sequence properties and classes
User:Charles R Greathouse IV/Rule of thumb	Sequences should take 1 hour to prepare for submission.
User:Charles R Greathouse IV/Standards	How to write up certain kinds of sequences.
User:Charles R Greathouse IV/Tables of special primes	Types of primes and their densities
User:Charles R Greathouse IV/To do	Sequences to work on and b-files to fix.
User:Charles R Greathouse IV/Vanity	Sequences named after their discoverer.
User:Charles R Greathouse IV/Wiki	Tools for the OEIS wiki.

Projects:

• Historical sequences
• The multi-faceted reach of the OEIS
• Sequences determined by prime signature

Useful links:

• Features Wishlist, User:Russ Cox/OEIS Server Features, Suggested Projects
• Deleted sequences (most recent month)
• Suggested pre-submit checklist
• Requested articles
• Editing history: sequence, wiki
• References on proof attempts: P vs. NP, Riemann hypothesis
• Resources: TME-EMT

Sequence of the Day

[talk]

Sequence of the Day for April 27

A024816: Antisigma (n):

x̅σ (n) := ∑ n i  = 1 i∤n i = tn  −  σ (n)

, for

n   ≥   1

.

{ 0, 0, 2, 3, 9, 9, 20, 21, 32, 37, ... }

For primes

p

,

x̅σ (  p) = t p  − 1  −  1 = p  (  p  − 1) 2  −  1

, where

t p  − 1

is the

(  p  −  1)

 -th triangular number. Compare with Euler's cototient function

x̅φ (n)

.

Sequences in the News

• Aug 17 2021 Swiss scientists announce they have calculated π (A000796) to 62.8 trillion digits in only 108 days.
• Dec 25 2018 German Heise-News "integers, please" column explains A003173 and OEIS.
• Feb 01 2018 Alphabet announced a $8,589,869,056 = $A000396(6) stock buyback.
• Jan 03 2018 Largest known term of A000043 announced: 77232917.
• Nov 18 2016 PrimeGrid proves that 10223 is not a Sierpinski number, since 10223 × 2 31172165 + 1 is prime. So no changes to A076336 for now.
• Sep 14 2016 Tom Greer discovers the twin primes 2996863034895 × 2 1290000 ± 1 using PrimeGrid, TwinGen and LLR.
• Jan 19 2016 Largest known term of A000043 announced: 74207281, also discovered by Curtis Cooper.

Complaints

I strive to live up to the highest ethical standards. If you feel that I have wrongly rejected one of your sequences (or otherwise failed to meet the expected standards), please leave a note at Complaints About Editing where it will be reviewed. I hope that in all cases you will first contact me (through the pink comment boxes, on my user page, or by email).