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 A171953 #3 Mar 30 2012 16:51:56 %S A171953 20,22,28,33,38,46,49,50,61,68,70,76,78,86,94,103,201,204,205,217,230, %T A171953 256,259,260,281,327,369,391,394,395,403,422,492,550,575,583,672,675, %U A171953 676,740,804,815,843,1103,1165,1488,1491,1492,1543,1668 %N A171953 Positions of 3's in A181391. %H A171953 N. J. A. Sloane, <a href="/A171953/b171953.txt">Table of n, a(n) for n = 1..143</a> %Y A171953 Cf. A181391, A171865, A171951-A171956. %K A171953 nonn %O A171953 1,1 %A A171953 _N. J. A. Sloane_, Oct 29 2010