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 A127287 #5 Mar 31 2012 13:21:13 %S A127287 0,1,2,3,4,5,6,7,8,9,11,10,12,13,14,15,16,17,18,19,20,21,22,23,28,24, %T A127287 30,33,25,29,26,31,32,27,34,35,36,37,39,38,40,41,42,43,44,45,46,47,48, %U A127287 49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,79,67,84,93,66,80 %N A127287 Signature-permutation of a Catalan automorphism: composition of A127285 and A057508. %C A127287 This automorphism permutes the top-level of a list of even length (1 ... 2n) as (1 2n 2 2n-1 3 2n-3 ... n n+1) and when applied to a list of odd length (1 .. 2n+1), permutes it as (1 2n+1 2 2n 3 2n-1 ... n n+1). Used to construct A127291. %H A127287 A. Karttunen, <a href="/A127287/b127287.txt">Table of n, a(n) for n = 0..2055</a> %H A127287 <a href="/index/Per#IntegerPermutationCatAuto">Index entries for signature-permutations of Catalan automorphisms</a> %o A127287 (Scheme implementation of this automorphism, destructive, that acts on S-expressions, i.e. list-structures:) %o A127287 (define (*A127287! s) (*A127285! (*A057508! s))) %Y A127287 Inverse: A127288. a(n) = A127285(A057508(n)). %K A127287 nonn %O A127287 0,3 %A A127287 _Antti Karttunen_, Jan 16 2007