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 A061337 #2 Mar 30 2012 18:51:34 %S A061337 0,1,-1,1,2,-1,1,2,-1,2,1,2,-1,2,3,1,2,3,2,3,4,1,2,-1,2,2,3,2,1,2,3,2, %T A061337 3,-1,2,3,1,2,2,2,3,3,2,2,3,1,2,3,2,2,3,2,3,3,3,1,2,2,2,3,2,2,3,3,2,2, %U A061337 1,2,3,2,2,3,2,2,3,3,2,3,1,2,3,2,3,2,2,3,3,2,2,3,3,1,2,2,2,3,3,2,3,2,2,2,2,3,3,1,2,3,2,3,3,2,2,3,2,2,3,3,3,2,1,2,3 %N A061337 Smallest number of distinct triangular numbers which sum to n (or -1 if not possible). %C A061337 20 is the only case where n>3. %e A061337 a(20)=4 since 20=1+3+6+10, a(21)=1 since 21 is triangular, a(22)=2 since 22=1+21, a(23)=-1 since no combination of distinct triangular numbers sum to 23. %Y A061337 Cf. A000217, A002243, A053614, A061208, A061336. %K A061337 sign %O A061337 0,5 %A A061337 _Henry Bottomley_, Apr 25 2001