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 A123497 #7 Mar 31 2012 13:21:12 %S A123497 0,1,2,3,4,6,7,5,8,9,10,14,16,19,17,18,12,11,13,20,15,21,22,23,24,25, %T A123497 26,27,37,38,42,44,47,51,53,56,60,45,46,48,49,50,31,32,30,28,29,34,33, %U A123497 35,36,54,55,40,39,41,57,43,58,59,61,52,62,63,64,65,66,67,68,69,70,71 %N A123497 Signature permutation of a nonrecursive Catalan automorphism: row 1655089 of table A089840. %H A123497 A. Karttunen, <a href="/A089840/a089840p.txt">Prolog-program which illustrates the construction of this and other similar nonrecursive Catalan automorphisms.</a> %H A123497 <a href="/index/Per#IntegerPermutationCatAuto">Index entries for signature-permutations of Catalan automorphisms</a> %o A123497 (Scheme function, destructive implementation of this automorphism acting on S-expressions:) (define (*A123497! s) (cond ((null? s) s) ((and (pair? (car s)) (pair? (cdar s))) (*A074680! s) (let ((old-cddr-s (cddr s))) (set-cdr! (cdr s) (cdadr s)) (set-cdr! (cadr s) old-cddr-s))) ((pair? (car s)) (*A072797! s)) ((pair? (cdr s)) (*A072796! s))) s) %Y A123497 Inverse: A123498. Row 1655089 of A089840. Used to construct automorphism *A123501. A074680(n) = A083927(a(A057123(n))). %K A123497 nonn %O A123497 0,3 %A A123497 _Antti Karttunen_, Oct 11 2006