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 A217917 #7 Mar 04 2013 18:31:56 %S A217917 1,5,9,11,15,17,27,29,39,41,47,49,55,61,65,69,73,79,85,89,93,111,117, %T A217917 119,125,137,149,153,155,161,175,181,191,193,195,211,227,231,243,255, %U A217917 267,269,275,279,287,295,301,307,315,317,329,335,347,349,355,357,359,361,365 %N A217917 Odd numbers that appear in sequence A217916. %H A217917 Paul D. Hanna, <a href="/A217917/b217917.txt">Table of n, a(n) for n = 1..286</a> %F A217917 a(n) = A217916( (n+1)*(n+2)/2 - 1 ) for n>=1. %Y A217917 Cf. A217916. %K A217917 nonn %O A217917 1,2 %A A217917 _Paul D. Hanna_, Mar 04 2013