A331985 a(n) is the least positive k such that n AND floor(n/k) = 0 (where AND denotes the bitwise AND operator).

1, 2, 2, 4, 2, 2, 4, 8, 2, 2, 2, 12, 4, 5, 8, 16, 2, 2, 2, 4, 2, 2, 12, 24, 4, 4, 5, 6, 8, 10, 16, 32, 2, 2, 2, 4, 2, 2, 4, 40, 2, 2, 2, 9, 12, 16, 24, 48, 4, 4, 4, 4, 5, 5, 6, 56, 8, 9, 10, 12, 16, 21, 32, 64, 2, 2, 2, 4, 2, 2, 4, 8, 2, 2, 2, 16, 4, 26, 40

Offset

0,2

Comments

This sequence has similarities with A261891; here we divide and round down, there we multiply, in order to obtain a number with no common bit with the original.

Links

Rémy Sigrist, Table of n, a(n) for n = 0..8192

Formula

a(n) = 2 iff n is a positive Fibbinary number (A003714).

Example

For n = 3:
- 3 AND floor(3/1) = 3,
- 3 AND floor(3/2) = 1,
- 3 AND floor(3/3) = 1,
- 3 AND floor(3/4) = 0,
- hence a(3) = 4.

Prog

(PARI) a(n) = for (k=1, oo, if (bitand(n, n\k)==0, return (k)))

Crossrefs

Cf. A003714, A261891, A332011.

Sequence in context: A115070 A064145 A213431 * A261891 A321320 A366808

Adjacent sequences: A331982 A331983 A331984 * A331986 A331987 A331988

Keyword

nonn,base

Author

Rémy Sigrist, Feb 03 2020

Status

approved