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 A131173 #5 Mar 31 2012 13:21:17 %S A131173 0,1,2,3,4,5,6,8,7,9,10,11,12,13,14,15,19,21,22,16,20,17,18,23,24,25, %T A131173 27,26,28,29,30,31,32,33,34,35,36,37,38,39,40,41,51,52,56,58,59,60,62, %U A131173 63,64,42,43,53,57,61,44,54,45,46,47,55,48,49,50,65,66,67,68,69,70,71 %N A131173 Signature permutation of a self-inverse Catalan automorphism: row 7 of A122285 and A122286. %C A131173 Derived from automorphism *A122282 with recursion scheme SPINE or ENIPS. %H A131173 A. Karttunen, <a href="/A131173/b131173.txt">Table of n, a(n) for n = 0..2055</a> %H A131173 <a href="/index/Per#IntegerPermutationCatAuto">Index entries for signature-permutations of Catalan automorphisms</a> %o A131173 (Destructive Scheme implementation of this automorphism, which acts on S-expressions, i.e. list-structures:) %o A131173 (define (*A131173! s) (cond ((pair? s) (*A069770! (car s)) (if (pair? (cdr s)) (*A131173! (cddr s))))) s) %K A131173 nonn %O A131173 0,3 %A A131173 _Antti Karttunen_, Jun 20 2007