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
Examples
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.
Links
- Rémy Sigrist, Table of n, a(n) for n = 0..8192
Programs
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PARI
a(n) = for (k=1, oo, if (bitand(n,n\k)==0, return (k)))
Formula
a(n) = 2 iff n is a positive Fibbinary number (A003714).
Comments