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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:
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 |
Sequence of the Day for October 11
A001020:11 n, n ≥ 0. |
- { 1, 11, 121, 1331, 14641, 161051, ... }
The decimal digits of the powers of 11 give binomial coefficients (which appear in Pascal’s triangle), until some binomial coefficients have more than one digit, where overlapping occurs.
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0 | 1 | | ||||||||||||||||
1 | 1 | 1 | | |||||||||||||||
2 | 1 | 2 | 1 | | ||||||||||||||
3 | 1 | 3 | 3 | 1 | | |||||||||||||
4 | 1 | 4 | 6 | 4 | 1 | | ||||||||||||
5 | 1 | 5 | 10 | 10 | 5 | 1 | ||||||||||||
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1 |
2 |
3 |
4 |
5 |
After 11 4 it doesn’t quite work out, since some binomial coefficients in {1, 5, 10, 10, 5, 1} have more than one decimal digits.
1, 5, 1 0, 1 0, 5, 1 ---------------- 1 6 1 0 5 1
In fact, the powers of 11 correspond to a Pascal’s triangle with only one digit per entry, and carry over to the next cell to the left in case of a value ≥ 10.
In general, ifb |
k |
(b + 1) n |
b |
(b + 1) k − 1 |
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).