A006774 Number of 2n-step polygons on honeycomb. (Formerly M2257)

1, 0, 0, 1, 0, 3, 2, 12, 18, 65, 138, 432, 1074, 3231, 8718, 25999, 73650, 220215, 643546, 1937877, 5783700, 17564727, 53222094, 163009086, 499634508, 1542392088, 4770925446, 14832934031, 46227584010, 144632622552, 453628244950

Offset

0,6

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

I. Jensen, Table of n, a(n) for n = 0..79

I. G. Enting and A. J. Guttmann, Polygons on the honeycomb lattice, J. Phys. A 22 (1989), 1371-1384.

I. Jensen, More terms

Formula

a(n) = A005396(n) / (2*n), n > 1. - Sean A. Irvine, Aug 06 2020

Crossrefs

Sequence in context: A167639 A113205 A136657 * A361865 A356857 A086551

Adjacent sequences: A006771 A006772 A006773 * A006775 A006776 A006777

Keyword

nonn

Author

N. J. A. Sloane

Extensions

a(0)-a(2) inserted by Sean A. Irvine, Aug 06 2020

Status

approved