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

Author

Rémy Sigrist, Jul 27 2018

Keywords

• nonn
• base

Comments

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

See A317420 for similar sequences.

Examples

			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.
		

Links

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

Crossrefs

Cf. A317420.

Programs

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] ", "))