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

1,3

Comments

See A317420 for similar sequences.

Links

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

Rémy Sigrist, Scatterplot of the first 500000 terms

Example

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.

Prog

(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 ", "))

Crossrefs

Cf. A070939, A317420.

Sequence in context: A082501 A249858 A249857 * A249777 A289065 A132815

Adjacent sequences: A317438 A317439 A317440 * A317442 A317443 A317444

Keyword

nonn,base

Author

Rémy Sigrist, Jul 28 2018

Status

approved