login
A331985
a(n) is the least positive k such that n AND floor(n/k) = 0 (where AND denotes the bitwise AND operator).
2
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
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
KEYWORD
nonn,base
AUTHOR
Rémy Sigrist, Feb 03 2020
STATUS
approved