A069788 Number of tilings by lozenges of hexagon with sides n, n+1, n, n+1, n, n+1 and central triangle removed.

2, 54, 4320, 2500000, 5252187500, 68336412238080, 3507134014317846528, 1039468958911770833166336, 1271288794044247678785011427072, 8629570422218326431392139107794299444, 248662702551142788293946930136251315440514048, 38763625610496798571986566181715696354290667009540096

Offset

1,1

References

J. Propp, Enumeration of matchings: problems and progress, pp. 255-291 in L. J. Billera et al., eds, New Perspectives in Algebraic Combinatorics, Cambridge, 1999 (see Problem 1).

Links

Table of n, a(n) for n=1..12.

J. Propp, Updated article

J. Propp, Enumeration of matchings: problems and progress, in L. J. Billera et al. (eds.), New Perspectives in Algebraic Combinatorics

Crossrefs

Sequence in context: A338514 A123686 A122418 * A283678 A306266 A117681

Adjacent sequences: A069785 A069786 A069787 * A069789 A069790 A069791

Keyword

nonn,easy

Author

N. J. A. Sloane, May 28 2002

Extensions

Propp gives 12 terms.

More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 30 2003

Status

approved