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 A185978 #19 Jul 25 2017 02:29:04
%S A185978 2,4,7,9,11,12,13,16,18,20,22,24,25,27,29,30,31,34,37,38,39,42,43,46,
%T A185978 48,49,51,56,57,58,60,61,64,65,67,69,70,72,73,76,79,81,83,84,87,88,90,
%U A185978 92,93,94,97,99,100,101,102,106,108
%N A185978 Nontriangular numbers which are the sum of two (positive) triangular numbers.
%C A185978 This is A051533 (sums of two positive triangular numbers) excluding triangular numbers.
%C A185978 This is also A020756 (sums of two triangular numbers) excluding triangular numbers.
%C A185978 There may be multiple representations, e.g., 16 = 1 + 15 = 6 + 10.
%H A185978 G. C. Greubel, <a href="/A185978/b185978.txt">Table of n, a(n) for n = 1..5000</a>
%F A185978 This is the sorted, made unique set {binomial(k+1,2) + binomial(L+1,2), 1 <= k <= L sufficiently large}, excluding members from A000217 (triangular numbers).
%e A185978 a(6) = 12 = 6 + 6,
%e A185978 a(17) = 31 = 3 + 28 = 10 + 21.
%t A185978 (* First run the program for A051533 *) Complement[%, tri] (* _Alonso del Arte_, Feb 15 2011 *)
%Y A185978 Cf. A000217, A020756 (sums of two triangular numbers), A051533 (sums of two positive triangular numbers).
%K A185978 nonn,easy
%O A185978 1,1
%A A185978 _Wolfdieter Lang_, Feb 14 2011