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Self-inverse permutation of nonnegative integers: a(n) = (A264987(n)-1) / 2.
10

%I #10 Dec 06 2015 21:14:06

%S 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 38,41,43,23,50,49,32,59,25,35,44,52,26,53,40,27,54,28,36,45,55,21,48,

%U 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 Self-inverse permutation of nonnegative integers: a(n) = (A264987(n)-1) / 2.

%H Antti Karttunen, <a href="/A264989/b264989.txt">Table of n, a(n) for n = 0..4921</a>

%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>

%F a(n) = (A264987(n)-1) / 2.

%F a(n) = (1/2) * (A263272((2*n)+1) - 1).

%F a(n) = (1/4) * (A263273(4n + 2) - 2).

%o (Scheme, two alternative definitions)

%o (define (A264989 n) (/ (- (A264987 n) 1) 2))

%o (define (A264989 n) (/ (- (A263273 (A016825 n)) 2) 4))

%Y Cf. A016825, A263272, A263273, A264987, A264991, A264992.

%Y Cf. also A264985.

%K nonn

%O 0,3

%A _Antti Karttunen_, Dec 05 2015