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 A118139 #10 Jul 21 2015 15:40:37 %S A118139 6,16,21,31,36,42,46,51,55,56,66,72,76,81,91,94,106,111,120,121,123, %T A118139 126,133,136,141,146,156,157,171,172,174,181,186,191,196,198,210,211, %U A118139 216,225,226,231,237,241,246,256,259,268,276,281,286,289,291,297,301,306 %N A118139 Numbers expressible as the sum of two triangular numbers in at least two different ways. %C A118139 A052343(a(n)) > 1; gives A020756 together with A119345. - _Reinhard Zumkeller_, May 15 2006 %H A118139 Reinhard Zumkeller, <a href="/A118139/b118139.txt">Table of n, a(n) for n = 1..10000</a> %e A118139 a(1) = 6 = 0 + 6 = 3 +3. %e A118139 a(2) = 16 = 1 + 15 = 6 + 10. %e A118139 a(3) = 21 = 0 + 21 = 6 + 15. %t A118139 Sort[Transpose[Select[Tally[Total/@(Union[Sort/@Tuples[Accumulate[ Range[ 0,30]],2]])],#[[2]]>1&]][[1]]] (* _Harvey P. Dale_, Jul 21 2015 *) %o A118139 (Haskell) %o A118139 a118139 n = a118139_list !! (n-1) %o A118139 a118139_list = filter ((> 1) . a052343) [0..] %o A118139 -- _Reinhard Zumkeller_, Jul 25 2014 %Y A118139 Cf. A020757, A000217. %Y A118139 Cf. A052343. %K A118139 easy,nonn %O A118139 1,1 %A A118139 _Greg Huber_, May 13 2006 %E A118139 More terms from _Reinhard Zumkeller_, May 15 2006