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 A305538 #13 Jun 06 2018 08:28:18 %S A305538 1,3,2,1,8,2,5,10,7,5,18,7,12,20,3,12,5,1,22,3,10,22,13,8,35,11,20,35, %T A305538 2,18,5,22,33,1,12,31,16,8,49,12,25,47,30,21,2,26,41,66,11,37,16,5,60, %U A305538 10,27,56,33,21,82,27,46,78,7,40,13,47,68,5,26,62,33 %N A305538 a(n) is the smallest positive generalized pentagonal number such that A001318(n) - a(n) is twice a generalized pentagonal number. %C A305538 Such a number exists for n >= 3 due to a theorem of Enge, Hart and Johansson (see the link, p. 11). %H A305538 Peter Luschny, <a href="/A305538/b305538.txt">Table of n, a(n) for n = 3..1000</a> %H A305538 Andreas Enge, William Hart and Fredrik Johansson, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL21/Enge/enge1.html">Short addition sequences for theta functions</a>, Journal of Integer Sequences, Vol. 21 (2018), Article 18.2.4. Also available as <a href="http://arxiv.org/abs/1608.06810">arXiv:1608.06810</a> [math.NT]. %e A305538 (A001318(328) - a(328))/2 = (40426 - 174)/2 = 20126 = A001318(231). %Y A305538 Cf. A001318, A305539. %K A305538 nonn %O A305538 3,2 %A A305538 _Peter Luschny_, Jun 04 2018