A383731 Number of hexagonal n-element polyominoes whose graph is a nonextensible path.

2, 3, 17, 41, 140, 389, 1182, 3369, 9817, 27903, 79936, 226784, 645730, 1831574, 5204271, 14766828, 41938778, 119061270

Offset: 13

Author

Bert Dobbelaere, May 07 2025

Keywords

• nonn
• more

Comments

A 2-sided strip polyhex is a shape formed by a set of connected cells on a hexagonal grid, all cells having exactly two neighbors except for the first and last cell, which have only one neighbor. The shape is considered identical to its mirror image, as well as any translation or rotation of itself. This sequence counts the number of 2-sided strip polyhexes with n cells to which no additional cell can be added without introducing a branch or cycle. See also illustration.

Links

• Bert Dobbelaere, Illustration of initial terms colored by symmetry
• Ed Pegg, Jr., Illustrations of polyforms
• Eric Weisstein's World of Mathematics, Polyhex

Crossrefs

Cf. A003104.