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 A264989 #10 Dec 06 2015 21:14:06 %S A264989 0,1,2,5,4,3,6,7,11,14,16,8,17,13,9,18,10,12,15,19,20,47,22,29,56,34, %T A264989 38,41,43,23,50,49,32,59,25,35,44,52,26,53,40,27,54,28,36,45,55,21,48, %U A264989 31,30,57,37,39,42,46,24,51,58,33,60,61,101,128,142,74,155,67,83,164,88,110,137,169,65,146,103,92,173,115,119,122 %N A264989 Self-inverse permutation of nonnegative integers: a(n) = (A264987(n)-1) / 2. %H A264989 Antti Karttunen, <a href="/A264989/b264989.txt">Table of n, a(n) for n = 0..4921</a> %H A264989 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A264989 a(n) = (A264987(n)-1) / 2. %F A264989 a(n) = (1/2) * (A263272((2*n)+1) - 1). %F A264989 a(n) = (1/4) * (A263273(4n + 2) - 2). %o A264989 (Scheme, two alternative definitions) %o A264989 (define (A264989 n) (/ (- (A264987 n) 1) 2)) %o A264989 (define (A264989 n) (/ (- (A263273 (A016825 n)) 2) 4)) %Y A264989 Cf. A016825, A263272, A263273, A264987, A264991, A264992. %Y A264989 Cf. also A264985. %K A264989 nonn %O A264989 0,3 %A A264989 _Antti Karttunen_, Dec 05 2015