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 A154122 #5 Mar 31 2012 13:21:17 %S A154122 0,1,2,3,5,4,6,7,8,12,13,9,10,11,15,14,16,17,18,19,20,21,22,31,32,34, %T A154122 35,36,23,24,25,26,27,28,29,30,33,40,41,37,38,39,43,42,44,45,46,47,48, %U A154122 49,50,52,51,53,54,55,56,57,58,59,60,61,62,63,64,87,88,90,91,92,96,97 %N A154122 Signature permutation of a Catalan bijection: row 3747 of A089840. %C A154122 This bijection of binary trees can be obtained by applying bijection *A074680 to the right hand side subtree and leaving the left hand side subtree intact. See also comments at A154121. %C A154122 .B...C...............C...D %C A154122 ..\./.................\./ %C A154122 ...x...D....-->....B...x.................()..C ........C...() %C A154122 ....\./.............\./...................\./....-->....\./... %C A154122 .A...x...........A...x.................A...x.........A...x.... %C A154122 ..\./.............\./...................\./...........\./..... %C A154122 ...x...............x.....................x.............x...... %C A154122 .............................................................. %C A154122 That is, (a . ((b . c) . d)) -> (a . (b . (c . d))) %C A154122 or (a . (() . c)) -> (a . (c . ())) if the former is not possible. %H A154122 A. Karttunen, <a href="/A154122/b154122.txt">Table of n, a(n) for n = 0..2055</a> %H A154122 <a href="/index/Per#IntegerPermutationCatAuto">Index entries for signature-permutations of Catalan automorphisms</a> %o A154122 (Destructive version of this automorphism in Scheme:) (define (*A154122! s) (if (pair? s) (*A074680! (cdr s))) s) %Y A154122 Inverse: A154121. a(n) = A069770(A089866(A069770(n))). Cf. A154124. %K A154122 nonn %O A154122 0,3 %A A154122 _Antti Karttunen_, Jan 06 2009