A066931 Number of ways to tile hexagon of edge n with diamonds of side 1, not counting rotations and reflections as different.

1, 1, 6, 113, 20174, 22306955, 123222909271, 3283834214485890, 421263391026827547540, 260028731850596651411721718, 772086476515163830856527013278243, 11025620741283840573496993339545350520150, 757129347300072898736973484532998417574513923224

Offset: 0

Author

R. K. Guy, Feb 05 2002

Keywords

• nonn

Links

• R. K. Guy and D. J. Reble, Illustration of initial terms
• P. J. Taylor, Counting distinct dimer hex tilings, Preprint, 2015.

Crossrefs

Cf. A008793.

Formula

From Peter J. Taylor, Jun 17 2015: (Start)

For odd n, a(n) = A008793(n)/12 + A049505(n)/4 + A006366(n)/6.

For even n, a(n) = A008793(n)/12 + A049505(n)/4 + A006366(n)/6 + A181119(n/2)/4 + A259049(n/2)/12 + A049503(n/2)/6.

See Taylor link.

(End)

Extensions

One more term from Don Reble, Feb 07 2002

More terms from Peter J. Taylor, Jun 17 2015