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 A154457 #4 Mar 31 2012 13:21:18 %S A154457 0,1,3,2,8,7,6,4,5,21,22,20,18,17,19,16,14,9,10,15,11,12,13,58,59,62, %T A154457 63,64,57,61,55,50,49,54,48,45,46,56,60,53,47,44,51,42,37,23,24,38,25, %U A154457 26,27,52,43,39,28,29,40,30,31,32,41,33,34,35,36,170,171,174,175,176 %N A154457 Signature-permutation of a Catalan bijection induced by wreath recursion a=s(b,c), b=s(c,a), c=(c,c), starting from state b. %C A154457 This Catalan bijection is induced by the second generator of group 2861 mentioned on page 144 of "Classification of groups generated by 3-state automata over a 2-letter alphabet" paper. Specifically, *A154457 = psi(A154447), where the isomorphism psi is given in A153141 (see further comments there). %H A154457 A. Karttunen, <a href="/A154457/b154457.txt">Table of n, a(n) for n = 0..2055</a> %H A154457 Bondarenko, Grigorchuk, Kravchenko, Muntyan, Nekrashevych, Savchuk, Sunic, <a href="http://arxiv.org/abs/0803.3555">Classification of groups generated by 3-state automata over a 2-letter alphabet</a>, p. 144. %H A154457 <a href="/index/Per#IntegerPermutationCatAuto">Index entries for signature-permutations of Catalan automorphisms</a> %o A154457 (Scheme function, destructive implementation of this automorphism acting on S-expressions:) (define (*A154457! s) (cond ((pair? s) (*A069770! s) (*A154458! (car s)))) s) %Y A154457 Inverse: A154458. a(n) = A057163(A154458(A057163(n))). %K A154457 nonn %O A154457 0,3 %A A154457 _Antti Karttunen_, Jan 17 2009