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 A180917 #9 Feb 16 2020 20:08:17 %S A180917 1,2,4,5,6,7,8,10,11,12,13,14,16,17,18,19,22,23,24,25,27,28,29,30,31, %T A180917 33,34,35,38,39,40,41,44,45,46,47,49,50,51,52,55,56,58,60,61,62,64,65, %U A180917 66,67,68,71,72,73,76,77,78,79,81,82,84,85,87,88,92,93,94,97,98,99,101 %N A180917 Numbers that are not the sum of three positive heptagonal numbers. %C A180917 Complement of A117105. This is to heptagonal numbers A000566, %C A180917 as A007536 is to hexagonal numbers A000384, %C A180917 as A003679 is to pentagonal numbers A000326, %C A180917 and as A004214 is to squares A000290. %C A180917 This sequence is presumably finite: what is its likely last element? %C A180917 Last element appears to be a(1671) = 273118. - _Charles R Greathouse IV_, Sep 27 2010 %H A180917 Charles R Greathouse IV, <a href="/A180917/b180917.txt">Table of n, a(n) for n = 1..1671</a> %Y A180917 Cf. A000290, A000326, A000384, A000566, A003679, A004214, A007536, A117105. %K A180917 easy,nonn %O A180917 1,2 %A A180917 _Jonathan Vos Post_, Sep 23 2010