A006535 Number of one-sided hexagonal polyominoes with n cells. (Formerly M2846)

1, 1, 3, 10, 33, 147, 620, 2821, 12942, 60639, 286190, 1364621, 6545430, 31586358, 153143956, 745700845, 3644379397, 17869651166, 87877879487, 433301253231

Offset

1,3

References

J. Meeus, personal communication.

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

Links

Table of n, a(n) for n=1..20.

J. Meeus & N. J. A. Sloane, Correspondence, 1974-1975

Ed Pegg, Jr., Illustrations of polyforms

Eric Weisstein's World of Mathematics, Polyhex

Formula

a(n) = 2*A000228(n) - A030225(n).

Crossrefs

Cf. A000228, A030225.

Sequence in context: A326558 A149031 A145928 * A041633 A308499 A034215

Adjacent sequences: A006532 A006533 A006534 * A006536 A006537 A006538

Keyword

nonn,hard,more,nice

Author

N. J. A. Sloane

Extensions

a(7)-a(12) from David W. Wilson

a(13) from Achim Flammenkamp, Feb 15 1999

a(14)-a(20) from Joseph Myers, Sep 21 2002

Status

approved