This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A168022 #22 Feb 16 2025 08:33:11
%S A168022 1,2,11,53,127,233,541,743,977,1871,3511,4001,4523,5077,9851,11503,
%T A168022 12377,14221,16193,19391,20521,21683,22877,24103,29327,30713,33581,
%U A168022 42953,55343,57241,63127,67211,80231,84827,91961,101921,104491,123377
%N A168022 Noncomposite numbers in the eastern ray of the Ulam spiral as oriented on the March 1964 cover of Scientific American.
%C A168022 Although 1 was not considered a prime number in Ulam's time, the March 1964 cover of Scientific American shows 1 highlighted in the same way as the primes.
%H A168022 G. C. Greubel, <a href="/A168022/b168022.txt">Table of n, a(n) for n = 0..1000</a>
%H A168022 Alonso del Arte, <a href="https://www.youtube.com/watch?v=dx24qqBc-PY">Ulam spiral</a> (2009). [Note that "East" and "West" in this video match the cover of Scientific American, but "North" and "South" are switched.]
%H A168022 BackIssues.com, <a href="http://backissues.com/issue/Scientific-American-March-1964">Scientific American March 1964 back issue</a>
%H A168022 MathWorld, <a href="https://mathworld.wolfram.com/PrimeSpiral.html">Prime Spiral</a>
%H A168022 Scientific American, <a href="/A168022/a168022.pdf">March 1964 cover</a>
%H A168022 Wikipedia, <a href="https://en.wikipedia.org/wiki/Ulam_spiral#Construction">Ulam Spiral</a>
%F A168022 Positive numbers of the form 4n^2 - 3n + 1 with no more than two divisors.
%t A168022 Select[Table[4 n^2 - 3 n + 1, {n, 0, 199}], Length[Divisors[ # ]] < 3 &]
%Y A168022 Cf. A054552, all numbers of the form 4n^2 - 3n + 1. Primes of northeastern ray are in A073337. Noncomposites of the northern ray are in A168023. Noncomposites of the northwestern ray are in A168024. Noncomposites of the western ray are in A168025. Noncomposites of the southwestern ray are in A168026. Noncomposites of the southern ray are in A168027.
%K A168022 easy,nonn
%O A168022 0,2
%A A168022 _Alonso del Arte_, Nov 16 2009