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# Main Page/Prototype

 Welcome to the OEIS wiki, the wiki complement to the On-Line Encyclopedia of Integer Sequences. 179,136 articles.

## Editor's Guide

• A239797 Decimal expansion of ${\displaystyle {\frac {\sqrt {3}}{\sqrt[{3}]{4}}}}$.
• A238271 Decimal expansion of ${\displaystyle \sum _{n=1}^{\infty }{\frac {\mu (n)}{3^{n}}}}$.
• A237042 UPC check digits.
• A236603 Lowest canonical Gray cycles of length ${\displaystyle 2n}$.
• A235365 Smallest odd prime factor of ${\displaystyle 3^{n}+1}$.
• A234522 Decimal expansion of ${\displaystyle {\sqrt[{4}]{7}}-{\sqrt[{4}]{5}}}$.
• A233748 Number of graphs on n vertices with edges colored with at most four interchangeable colors under the symmetries of the full edge permutation group.
• A232499 Number of unit squares, aligned with a Cartesian grid, completely within the first quadrant of a circle centered at the origin ordered by increasing radius.
• A231963 Concatenate ${\displaystyle n}$ with its UPC check digit.
• A230624 Numbers ${\displaystyle n}$ with property that for every base ${\displaystyle b\geq 2}$, there is a number ${\displaystyle m}$ such that ${\displaystyle m+s(m)=n}$, where ${\displaystyle s(m)}$ is the sum of digits in the base ${\displaystyle b}$ expansion of ${\displaystyle m}$.

## Sequence of the Day for February 22

A008604: Multiples of
 22
.
 { 22, 44, 66, 88, 110, 132, 154, ... }
An even number that is divisible by
 22
is obviously divisible by
 11
. (In base
 10
, a number is divisible by
 11
if and only if the sum of "digits" in base
 100
is divisible by
 11
, e.g.
 1 + 10 = 11, 1 + 32 = 33, 1 + 54 = 55, ..., 2 + 14 + 94 = 110
implies that
 110, 132, 154, ..., 21494
are divisible by
 11
.)

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## On this day...

• February 22, 1805 Siméon Denis Poisson officially nominates François Arago to help him measure the meridian.
• February 22, 1930 Frank Plumpton Ramsey is born in Cambridge.

## Sequences in the News

• November 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.
• September 14, 2016 Tom Greer discovers the twin primes 2996863034895 × 2 1290000 ± 1 using PrimeGrid, TwinGen and LLR.
• January 19, 2016 Largest known term of A000043 announced: 274207281, also discovered by Curtis Cooper.
• March 2, 2014 Fredrik Johansson announces a computation of the partition number ${\displaystyle \scriptstyle p(10^{20})\approx 1.8381765\cdot 10^{11140086259}}$, the largest known term of A000041.
• December 6, 2013 Microsoft launches a challenge to find large non-Mersenne primes, A138837.
• May 13, 2013 H. A. Helfgott submits a proof of the weak Goldbach conjecture, i.e. for odd numbers as sums of three primes: A007963 has no more zeroes.
• January 25, 2013 Curtis Cooper discovers a new member of A000043, 57885161. Its index is not known but is at least 48.
• January 13, 2013 The winners of the contest for new sequences in the OEIS at JMM 2013 were announced: A187824, A187771, and A187761.

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