A317419 a(n) = number of k with 1 <= k <= n-1 such that a(k) AND a(n-k) = 0 (where AND denotes the bitwise AND operator).

0, 1, 2, 2, 4, 4, 4, 6, 8, 8, 6, 6, 8, 8, 8, 10, 12, 12, 10, 14, 20, 14, 8, 10, 12, 12, 8, 8, 12, 14, 14, 10, 10, 12, 12, 8, 10, 14, 16, 12, 6, 10, 12, 14, 8, 8, 12, 14, 14, 14, 14, 10, 12, 12, 8, 12, 18, 16, 12, 8, 10, 14, 18, 14, 10, 18, 18, 16, 12, 14, 18

Offset

1,3

Comments

All terms are even except a(2) = 1.

See A317420 for similar sequences.

Links

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Example

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

Prog

(PARI) a = vector(71); for (n=1, #a, a[n] = sum(k=1, n-1, bitand(a[k], a[n-k])==0); print1 (a[n] ", "))

Crossrefs

Cf. A317420.

Sequence in context: A333787 A062570 A108514 * A364843 A372678 A120456

Adjacent sequences: A317416 A317417 A317418 * A317420 A317421 A317422

Keyword

nonn,base

Author

Rémy Sigrist, Jul 27 2018

Status

approved