A317441 a(n) = number of k with 1 <= k <= n-1 such that a(k) and a(n-k) have the same binary length (A070939).

0, 1, 2, 1, 2, 3, 0, 5, 4, 1, 6, 3, 0, 5, 4, 1, 10, 5, 2, 7, 0, 7, 10, 5, 6, 7, 2, 5, 8, 5, 8, 7, 10, 9, 6, 7, 8, 7, 10, 11, 6, 7, 8, 11, 6, 17, 8, 9, 8, 19, 8, 13, 10, 15, 6, 19, 10, 9, 6, 19, 8, 13, 14, 13, 10, 17, 14, 15, 10, 19, 14, 9, 16, 15, 10, 11, 20

Offset: 1

Author

Rémy Sigrist, Jul 28 2018

Keywords

• nonn
• base

Comments

See A317420 for similar sequences.

Examples

			For n = 4:
- A070939(a(1)) = 1 <> 2 = A070939(a(3)),
- A070939(a(2)) = 1 =  1 = A070939(a(2)),
- A070939(a(3)) = 2 <> 1 = A070939(a(1)),
- hence a(4) = 1.
		

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..10000
• Rémy Sigrist, Scatterplot of the first 500000 terms

Crossrefs

Cf. A070939, A317420.

Programs

PARI

l = vector(77); for (n=1, #l, l[n] = #binary(max(1, v=sum(k=1, n-1, l[k]==l[n-k]))); print1 (v ", "))