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 A115511 #7 Apr 09 2014 10:12:22 %S A115511 1,3,2,5,6,4,7,9,8,10,11,12,13,14,15,17,16,18,19,20,21,22,23,24,25,26, %T A115511 27,28,29,30,31,33,32,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49, %U A115511 50,51,52,53,54,55,56,57,58,59,60,61,62,63,65,64,66,67,68,69,70,71,72 %N A115511 Inverse permutation to sequence A115510. %e A115511 A115510(4) = 6, hence a(6) = 4; A115510(5) = 4, hence a(4) = 5; A115510(6) = 5, hence a(5) = 6. %Y A115511 Cf. A115510. %K A115511 easy,nonn %O A115511 1,2 %A A115511 _Leroy Quet_, Jan 23 2006 %E A115511 Corrected and extended by _Klaus Brockhaus_, Jan 24 2006