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

0,3

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

Formula

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

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

Prog

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

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.

Sequence in context: A336564 A129468 A236846 * A091703 A004180 A011418

Adjacent sequences: A236844 A236845 A236846 * A236848 A236849 A236850

Keyword

nonn

Author

Antti Karttunen, Jan 31 2014

Status

approved