A236837 The greatest inverse of A234741: a(n) = the largest k such that A234741(k) = n, and 0 if no such k exists.

0, 1, 2, 3, 4, 9, 6, 7, 8, 21, 18, 11, 12, 13, 14, 27, 16, 81, 42, 19, 36, 49, 22, 39, 24, 0, 26, 63, 28, 33, 54, 31, 32, 93, 162, 91, 84, 37, 38, 99, 72, 41, 98, 43, 44, 189, 78, 47, 48, 77, 0, 243, 52, 57, 126, 0, 56, 117, 66, 59, 108, 61, 62, 147, 64, 441, 186, 67, 324, 121

Offset

0,3

Comments

A234741(a(n)) = n, unless n is in A236834, in which case a(n)=0.

For all n, a(n) <= A234742(n). A236850 gives such k that a(k) = A234742(k).

If n is in A236835, a(n) > A236836(n), otherwise a(n) = A236836(n).

a(2^n) = 2^n.

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

Links

Antti Karttunen, Table of n, a(n) for n = 0..8192

Prog

(Scheme, finding the greatest inverse empirically with a naive loop. A234742 gives an absolute upper bound for any inverse of A234741):
(define (A236837 n) (let ((u (A234742 n))) (let loop ((i u)) (let ((k (A234741 i))) (cond ((< i n) 0) ((= k n) i) (else (loop (- i 1))))))))

Crossrefs

A236834 gives the positions of zeros.

Differs from A235042 and A234742 for the first time at n=25, where a(25)=0 but A235042(25)=5 and A234742(25)=25.

Cf. A236836 (the least inverse of A234741).

Cf. also A236833, A236835, A234741, A236841, A236850.

Sequence in context: A352728 A236852 A363318 * A235042 A234742 A277711

Adjacent sequences: A236834 A236835 A236836 * A236838 A236839 A236840

Keyword

nonn

Author

Antti Karttunen, Jan 31 2014

Status

approved