A236836 - OEIS

%I #9 Feb 07 2014 10:44:35

%S 0,1,2,3,4,5,6,7,8,21,10,11,12,13,14,15,16,17,42,19,20,49,22,23,24,0,

%T 26,35,28,29,30,31,32,93,34,91,84,37,38,55,40,41,98,43,44,105,46,47,

%U 48,77,0,51,52,53,70,0,56,65,58,59,60,61,62,147,64,245,186,67,68,121

%N The least inverse of A234741: a(n) = the smallest k such that A234741(k) = n, and 0 if no such k exists.

%C A234741(a(n)) = n if n is not in A236834, in which case a(n)=0.

%H Antti Karttunen, <a href="/A236836/b236836.txt">Table of n, a(n) for n = 0..8192</a>

%F a(2^n) = 2^n.

%F a(2n) = 2*a(n).

%F If n is in A236835, a(n) < A236837(n), otherwise a(n) = A236837(n).

%o (Scheme, finding the smallest inverse empirically with a naive loop. A234742 gives an absolute upper bound for any inverse of A234741):

%o (define (A236836 n) (let ((u (A234742 n))) (let loop ((i 0)) (let ((k (A234741 i))) (cond ((> k u) 0) ((= k n) i) (else (loop (+ i 1))))))))

%Y A236834 gives the positions of zeros.

%Y Cf. A236833, A236835, A236837 (the greatest inverse of A234741).

%K nonn

%O 0,3

%A _Antti Karttunen_, Jan 31 2014