A137193 Number of n-celled polyhexes with perimeter < 4n+2.

0, 0, 1, 2, 10, 46, 215, 1037, 5083, 24918, 122437, 601980, 2960751, 14572369, 71782670, 353971120, 1747541596, 8638634526, 42760422695, 211948528089, 1051986803699, 5228475770699, 26020309838786, 129660152324728

Offset

1,4

Comments

These are n-cell polyhexes with the perimeter less than the maximum possible one.

If we associate a graph to a polyhex with vertices representing cells and edges representing two cells with a common edge, then this sequence enumerates polyhexes whose corresponding graphs have cycles.

Links

Table of n, a(n) for n=1..24.

Formula

a(n) = A000228(n) - A038142(n).

Crossrefs

Cf. A000228, A038142.

Sequence in context: A106709 A204091 A221196 * A006213 A137635 A029706

Adjacent sequences: A137190 A137191 A137192 * A137194 A137195 A137196

Keyword

nonn,hard,more

Author

Tanya Khovanova, Mar 03 2008

Extensions

a(12)-a(24) from Bert Dobbelaere, Mar 12 2026 (using formula)

Status

approved