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 A054426 #9 Aug 20 2013 05:12:39
%S A054426 1,2,3,4,7,8,5,6,13,19,14,15,20,16,9,10,23,34,29,35,50,43,24,25,44,53,
%T A054426 38,30,39,26,11,12,33,59,48,66,97,84,49,60,108,132,98,86,109,75,36,37,
%U A054426 76,112,89,99,135,113,61,54,91,100,69,55,62,40,17,18,47,82,73,105,154
%N A054426 Inverse permutation to A054424.
%H A054426 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%F A054426 a(j) = nthmember(j, A054424)
%p A054426 nthmember := proc(e,l) local k; if(member(e,l,'k')) then RETURN(k) else RETURN(0); fi; end;
%t A054426 a[n_] := If[p = Position[A054424, n]; p != {}, p[[1, 1]], 0]; (* _Jean-François Alcover_, Aug 20 2013 *)
%K A054426 nonn
%O A054426 1,2
%A A054426 Antti Karttunen