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 A154452 #4 Mar 31 2012 13:21:17 %S A154452 0,1,3,2,7,8,6,4,5,17,18,20,21,22,16,19,14,10,9,15,11,12,13,45,46,48, %T A154452 49,50,54,55,57,58,59,61,62,63,64,44,47,53,56,60,42,51,38,26,27,37,25, %U A154452 23,24,43,52,39,29,28,40,30,31,32,41,33,34,35,36,129,130,132,133,134 %N A154452 Signature permutation of a Catalan bijection: The inverse of A154451. %C A154452 This automorphism of rooted plane binary trees switches the two descendant trees for every other vertex as it descends along the 111... ray, starting swapping already at the root. Specifically, *A154452 = psi(A154442), where the isomorphism psi is given in A153141 (see further comments there). %H A154452 A. Karttunen, <a href="/A154452/b154452.txt">Table of n, a(n) for n = 0..2055</a> %H A154452 <a href="/index/Per#IntegerPermutationCatAuto">Index entries for signature-permutations of Catalan automorphisms</a> %o A154452 (Scheme function, destructive implementation of this automorphism acting on S-expressions:) (define (*A154452! s) (cond ((pair? s) (*A069770! s) (*A154450! (cdr s)))) s) %Y A154452 Inverse: A154451. a(n) = A069767(A154454(n)) = A057163(A154456(A057163(n))). Cf. A069770, A154450. %K A154452 nonn %O A154452 0,3 %A A154452 _Antti Karttunen_, Jan 17 2009