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 A185979 #11 May 09 2021 10:57:29 %S A185979 16,31,42,46,51,56,72,76,81,94,106,111,121,123,126,133,141,146,156, %T A185979 157,172,174,181,186,191,196,198,211,216,225,226,231,237,241,246,256, %U A185979 259,268,276,281,286,289,291,297,301,306,310,315,321,326,328,331,336,342,346,354,361,366,367 %N A185979 Numbers which are the sum of two positive triangular numbers in more than one way. %C A185979 This is a subsequence of A020756 (sums of two triangular numbers). %C A185979 This is also a subsequence of A051533 (sums of two positive triangular numbers). This is not a subsequence of A185978 (nontriangular numbers as sums of (positive) triangular numbers). E.g., a(32)=231 is missing there because 231=A000217(21). See A185980. %C A185979 For the numbers which are sums of two positive triangular numbers in exactly two ways see A064816. %C A185979 The first number which can be written in exactly three ways as sums of positive triangular numbers is 81. %C A185979 a(n) gives the positions where A052344 entries are >= 2: A052344(a(n)) >= 2. %H A185979 T. D. Noe, <a href="/A185979/b185979.txt">Table of n, a(n) for n = 1..1000</a> %e A185979 16 = 15 + 1 = 10 + 6. %e A185979 81 = 45 + 36 = 66 + 15 = 78 + 3. %e A185979 231= 210 + 21 = 153 + 78 %Y A185979 Cf. A000217, A020756, A051533, A052344, A064816, A185980. %K A185979 nonn,easy %O A185979 1,1 %A A185979 _Wolfdieter Lang_, Feb 15 2011