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 A127288 #5 Mar 31 2012 13:21:13 %S A127288 0,1,2,3,4,5,6,7,8,9,11,10,12,13,14,15,16,17,18,19,20,21,22,23,25,28, %T A127288 30,33,24,29,26,31,32,27,34,35,36,37,39,38,40,41,42,43,44,45,46,47,48, %U A127288 49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,70,67,72,75,79,81 %N A127288 Signature-permutation of a Catalan automorphism: composition of A057508 and A127286. %C A127288 This automorphism permutes the top-level of a list of even length (1 ... 2n) as (1 3 5 2n-1 ... 2n 2n-2 ... 4 2) and when applied to a list of odd length (1 .. 2n+1), permutes it as (1 3 5 2n-1 2n+1 2n 2n-2 ... 4 2). %H A127288 <a href="/index/Per#IntegerPermutationCatAuto">Index entries for signature-permutations of Catalan automorphisms</a> %o A127288 (Scheme implementation of this automorphism, destructive, that acts on S-expressions, i.e. list-structures:) %o A127288 (define (*A127288! s) (*A057508! (*A127286! s))) %Y A127288 Inverse: A127287. a(n) = A057508(A127286(n)). %K A127288 nonn %O A127288 0,3 %A A127288 _Antti Karttunen_, Jan 16 2007