A364830 a(n) is the number of line intersections (not coinciding with a vertex) inside a regular n-gon after inscribing (always starting from the same point), for each proper divisor d_i of n greater than 1, a regular d_i-gon.

0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 9, 0, 1, 4, 0, 0, 8, 0, 11, 4, 1, 0, 29, 0, 1, 0, 11, 0, 43, 0, 0, 4, 1, 8, 50, 0, 1, 4, 39, 0, 49, 0, 11, 24, 1, 0, 73, 0, 12, 4, 11, 0, 33, 8, 43, 4, 1, 0, 193, 0, 1, 28, 0, 8, 57, 0, 11, 4, 71, 0, 164, 0, 1, 28, 11, 12, 61

Offset: 1

Author

Paolo Xausa, Aug 09 2023

Keywords

• nonn

Comments

Inspired by an X (or Twitter) post by Matt Henderson (see links section).

Links

• Matt Henderson, X post, 2023.
• Paolo Xausa, Illustration of first terms.
• Paolo Xausa, Illustration of a(60).

Crossrefs

Cf. A006561, A007569, A032741, A364828, A364829, A364838.

Formula

a(n) = 0 if n is prime, a power of 2 or A032741(n) <= 2.

a(n) = A364838(n) - n.