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 A172437 #10 Apr 25 2016 11:45:30 %S A172437 42,82,171,411,522,886,1042,1066,1183,1341,2596,2842,3480,3831,5012, %T A172437 5316,5360,5786,6219,6650,6924,8406,8666,9408,10707,11735,12590,12891, %U A172437 14422,14646,14826,17351,17702,17757,18882,23210,24108,25127,28175,31980,32400 %N A172437 Indices of pentagonal pyramidal numbers which are the sum of two other such numbers: k such that A002411(k) = A002411(i)+A002411(j) for some i,j>0. %C A172437 The numbers themselves are listed in A172425. This answers a question posed in A133459. %H A172437 Donovan Johnson, <a href="/A172437/b172437.txt">Table of n, a(n) for n = 1..160</a> %e A172437 a(1)=42 because A002411(42) is the smallest term in that sequence which is the sum of two other (nonzero) terms of A002411. %o A172437 (PARI) for(n=1,99999,for(m=1,n-1, isA002411(p(n)-p(m)) & !print1(n", ") & break)) /* needs isA002411() and p() */ %Y A172437 Cf. A133459, A172425. %K A172437 nonn %O A172437 1,1 %A A172437 _M. F. Hasler_, Nov 20 2010