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

13,1

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

Table of n, a(n) for n=13..30.

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, A359521.

Sequence in context: A042137 A067976 A154316 * A051084 A106860 A042699

Adjacent sequences: A383728 A383729 A383730 * A383732 A383733 A383734

Keyword

nonn,more

Author

Bert Dobbelaere, May 07 2025

Status

approved