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A066931 Number of ways to tile hexagon of edge n with diamonds of side 1, not counting rotations and reflections as different. 2
1, 1, 6, 113, 20174, 22306955, 123222909271, 3283834214485890, 421263391026827547540, 260028731850596651411721718, 772086476515163830856527013278243, 11025620741283840573496993339545350520150, 757129347300072898736973484532998417574513923224 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..12.

R. K. Guy and D. J. Reble, Illustration of initial terms

P. J. Taylor, Counting distinct dimer hex tilings, Preprint, 2015.

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)

CROSSREFS

Cf. A008793.

Sequence in context: A275924 A288561 A291917 * A324669 A051228 A194132

Adjacent sequences:  A066928 A066929 A066930 * A066932 A066933 A066934

KEYWORD

nonn

AUTHOR

R. K. Guy, Feb 05 2002

EXTENSIONS

One more term from Don Reble, Feb 07 2002

More terms from Peter J. Taylor, Jun 17 2015

STATUS

approved

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Last modified October 18 08:01 EDT 2019. Contains 328146 sequences. (Running on oeis4.)