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 A292564 #17 Sep 20 2017 20:08:32 %S A292564 0,3,4,10,11,12,21,22,23,24,36,37,38,39,40,55,56,57,58,59,60,78,79,80, %T A292564 81,82,83,84,105,106,107,108,109,110,111,112,136,137,138,139,140,141, %U A292564 142,143,144,171,172,173,174,175,176,177,178,179,180,210,211,212 %N A292564 Take 1, skip 3 * 1 - 1, take 2, skip 3 * 2 - 1, take 3, skip 3 * 3 - 1, ... %H A292564 Seiichi Manyama, <a href="/A292564/b292564.txt">Table of n, a(n) for n = 0..10000</a> %H A292564 Michael Boardman, <a href="http://www.jstor.org/stable/2691496">Proof Without Words: Pythagorean Runs</a>, Math. Mag., 73 (2000), 59. %F A292564 a(n) = n + floor((sqrt(8*n+1)-1)/2)*(3*floor((sqrt(8*n+1)-1)/2)+1)/2. - _Robert Israel_, Sep 20 2017 %p A292564 seq(seq(2*k^2+k+j,j=0..k),k=0..10); # _Robert Israel_, Sep 20 2017 %Y A292564 Cf. A059255, A063656, A292565. %K A292564 nonn,easy %O A292564 0,2 %A A292564 _Seiichi Manyama_, Sep 19 2017