Natural numbers, pairs reversed: a(n) = n + (-1)^n; also Nimsum n + 1.
1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 17, 16, 19, 18, 21, 20, 23, 22, 25, 24
2 seqfan posts
Wed Apr 8 00:55:37 CEST 2009 [seqfan] Re: Symmetric Relations and Self-Inverse Permutations