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# User:Charles R Greathouse IV

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

I can be contacted via my Talk page here, or by email: my first name (charles) at my initials (crg4) dot com. Other email addresses may work as well.

 User:Charles R Greathouse IV/Tables of special primes Types of primes and their densities User:Charles R Greathouse IV/Rule of thumb Sequences should take 1 hour to prepare for submission. User:Charles R Greathouse IV/Chase sequences 'Chase sequences': Axxxxxx refers to Ayyyyyy, which refers to Azzzzzz... User:Charles R Greathouse IV/Programs Programs in the OEIS: types, format, etc. User:Charles R Greathouse IV/Properties Sequence properties and classes User:Charles R Greathouse IV/Metadata Plans for OEIS metadata: keywords, categories, the index, etc. User:Charles R Greathouse IV/Favorites Some of my favorite sequences. User:Charles R Greathouse IV/Keywords Information on keywords: when to use them, new ones to add, etc. User:Charles R Greathouse IV/To do Sequences to work on and b-files to fix. 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/Pari Some Pari tools. User:Charles R Greathouse IV/Wiki Tools for the OEIS wiki.

Projects:

[talk]

## Sequence of the Day for July 31

A173419: Length of shortest computation yielding $\scriptstyle n,\, n \,\ge\, 1, \,$ using addition, subtraction and multiplication.

 { 0, 1, 2, 2, 3, 3, 4, 3, 3, 4, 4, 4, 5, ... }

So you start with $\scriptstyle x_0 \,=\, 1,\, x_m \,=\, n \,$ and then through successive $\scriptstyle x_k \,=\, x_i + x_j \,$, $\scriptstyle x_k \,=\, x_i x_j \,$, or $\scriptstyle x_k \,=\, x_i - x_j \,$ operations for some $\scriptstyle 0 \,\le\, i,\, j \,<\, k \,$, you get to $\scriptstyle n \,$. The fun is of course getting there in as few steps as possible. Prime $\scriptstyle n \,$ are not necessarily more difficult to get to than their neightbors: 29, for example, requires five operations, just as 28 and 30 do.

## Sequences in the News

• March 2, 2014 Fredrik Johansson announces he's computed p(1020), which he says is approximately 1.8381765 × 1011140086259. Once confirmed and verified, it will be 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 paper in which he claims to have proved the weak Goldbach conjecture, i.e. for odd numbers as sums of three primes. If true, then A007963 has no more zeroes. (The strong Goldbach conjecture, i.e. for even numbers as sums of two primes, has not been proved... yet!)
• 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.
• September 21, 2012 Nick Berry, founder of Data Genetics, finds that the 17th most common 10-digit ATM PIN is 3141592654 (see A011546).
• June 5, 2012. A transit of Venus is viewable from Earth. The next one won't be until the year 2117 = A171467(55).
• November 20, 2011. The OEIS adds its two hundred thousandth sequence, A200000.
• March 14, 2011 Michael Hartl argues $\scriptstyle \pi \,\approx\, 3.14159 \,$ (see A000796) should be replaced with $\scriptstyle \tau \,=\, 2 \pi \,\approx\, 6.2831853 \,$ (see A019692) as the more important constant.

## 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).