A185980 - OEIS

%I #10 Dec 01 2016 01:39:43

%S 16,31,42,46,51,56,72,76,81,94,106,111,121,123,126,133,141,146,156,

%T 157,172,174,181,186,191,196,198,211,216,225,226,237,241,246,256,259,

%U 268,281,286,289,291,297,301,306,310,315,321,326,328,331,336,342,346,354

%N Nontriangular numbers that are the sum of two (positive) triangular numbers in more than one way.

%C A000217(0)=0, but it will not appear as a summand.

%C A185979 uses only positive triangular summands, and includes triagonal (or body diagonal) numbers like 231, 276, 406, 666, ...

%F See the one given for A185978, taking into account multiplicities.

%e 16 = 15 + 1 = 10 + 6.

%e 81 = 45 + 36 = 66 + 15 = 78 + 3.

%Y Cf. A000217, A020756 (sums of two triangular numbers), A051533 (sums of two positive triangular numbers), A064816, A185978, A185979.

%K nonn,easy

%O 1,1

%A _Wolfdieter Lang_, Feb 15 2011