A285727 - OEIS

%I #11 Apr 25 2017 11:47:56

%S 0,0,1,1,2,2,3,2,2,3,5,3,7,5,3,4,11,4,13,5,5,7,17,6,4,11,4,7,19,6,23,

%T 8,7,13,6,9,29,17,11,10,31,10,37,11,6,19,41,12,9,9,13,13,43,8,10,14,

%U 17,23,47,15,53,29,10,16,14,14,59,17,19,15,61,18,67,31,9,19,15,22,71,20,8,37,73,21,22,41,23,22,79,12,21,23,29,43,26,24,83,25,14

%N a(1) = a(2) = 0, and for n > 2, a(n) = A252463(A252463(n)).

%C For n >= 3, a(n) gives the contents of the grandparent node of the node containing n in binary trees like A005940 and A163511.

%C Each number larger than one occurs exactly four times in this sequence.

%H Antti Karttunen, <a href="/A285727/b285727.txt">Table of n, a(n) for n = 1..8192</a>

%F a(1) = a(2) = 0, and for n > 2, a(n) = A252463(A252463(n)).

%F For n > 2, if n is even, a(n) = A252463(n/2), otherwise a(n) = A252463(A064989(n)).

%o (Scheme)

%o (define (A285727 n) (if (<= n 2) 0 (A252463 (A252463 n))))

%Y Cf. A005940, A064989, A163511, A252463, A285728.

%K nonn

%O 1,5

%A _Antti Karttunen_, Apr 25 2017