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 A154451 #11 Nov 18 2016 14:04:48 %S A154451 0,1,3,2,7,8,6,4,5,18,17,20,21,22,16,19,14,9,10,15,11,12,13,49,50,48, %T A154451 45,46,55,54,57,58,59,61,62,63,64,47,44,53,56,60,42,51,37,23,24,38,25, %U A154451 26,27,43,52,39,28,29,40,30,31,32,41,33,34,35,36,143,142,146,147,148 %N A154451 Signature permutation of a Catalan bijection induced by generator "b" of the rightward recursing instance of Basilica group wreath recursion: a = (1,b), b = s(1,a). %C A154451 This automorphism of rooted plane binary trees switches the two descendant trees for every other vertex as it returns back toward the root, after descending down to the rightmost tip of the tree along the 111... ray, so that the last vertex whose descendants are swapped is the root node of the tree. Specifically, *A154451 = psi(A154441), where the isomorphism psi is given in A153141 (see further comments there). %H A154451 A. Karttunen, <a href="/A154451/b154451.txt">Table of n, a(n) for n = 0..2055</a> %H A154451 <a href="/index/Per#IntegerPermutationCatAuto">Index entries for signature-permutations of Catalan automorphisms</a> %o A154451 (Scheme function, destructive implementation of this automorphism acting on S-expressions:) (define (*A154451! s) (cond ((pair? s) (*A154449! (cdr s)) (*A069770! s))) s) %Y A154451 Inverse: A154452. a(n) = A154453(A069768(n)) = A057163(A154455(A057163(n))). Cf. A069770, A154449. %K A154451 nonn %O A154451 0,3 %A A154451 _Antti Karttunen_, Jan 17 2009