A364838 a(n) is the number of line intersections (including vertices) 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.

1, 2, 3, 4, 5, 7, 7, 8, 9, 11, 11, 21, 13, 15, 19, 16, 17, 26, 19, 31, 25, 23, 23, 53, 25, 27, 27, 39, 29, 73, 31, 32, 37, 35, 43, 86, 37, 39, 43, 79, 41, 91, 43, 55, 69, 47, 47, 121, 49, 62, 55, 63, 53, 87, 63, 99, 61, 59, 59, 253, 61, 63, 91, 64, 73, 123, 67

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, A364830.

Formula

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

a(n) = A364830(n) + n.