A236847 Greatest inverse of A234742: a(n) = maximal k such that when it is remultiplied "upwards", from GF(2)[X] to N, the result is n, and 0 if no such k exists.

0, 1, 2, 3, 4, 0, 6, 7, 8, 5, 0, 11, 12, 13, 14, 0, 16, 0, 10, 19, 0, 9, 22, 0, 24, 25, 26, 15, 28, 0, 0, 31, 32, 29, 0, 0, 20, 37, 38, 23, 0, 41, 18, 0, 44, 0, 0, 47, 48, 21, 50, 0, 52, 0, 30, 55, 56, 53, 0, 59, 0, 61, 62, 27, 64, 0, 58, 67, 0, 0, 0, 0, 40, 73, 74, 43, 76, 49, 46, 0, 0, 17, 82, 0, 36, 0, 0, 87, 88, 0, 0, 91

Offset: 0

Author

Antti Karttunen, Jan 31 2014

Keywords

• nonn

Comments

Apart from zero, each term occurs at most once. 35 is the smallest positive integer not present in this sequence.

Links

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

Crossrefs

Differs from A236846 for the first time at n=91, where a(91) = 91, while A236846(91) = 35.

A236844 gives the positions of zeros.

Cf. A234742.

Cf. also A236836, A236837.

Programs

Scheme

(define (A236847 n) (let loop ((i n)) (cond ((zero? i) i) ((= (A234742 i) n) i) (else (loop (- i 1))))))

Formula

a(n) = maximal k such that A234742(k) = n, and 0 if no such k exists.

For all n, a(n) <= n.