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A056783 Number of diamond polyominoes with n cells. 3
1, 1, 3, 7, 20, 62, 204, 709, 2526, 9212, 33989, 126838, 476597, 1802618, 6850969, 26153537, 100207548, 385225375, 1485216987, 5741272625, 22246000726, 86383442996, 336093551268, 1309998354125, 5114452295933, 19998173607505, 78306014924606, 307022185565345 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Also the number of polybricks of size n made of Lego.

LINKS

Table of n, a(n) for n=1..28.

Ed Pegg, Jr., Illustrations of polyforms

M. Keller, More information

M. Vicher, Polyforms

Eric Weisstein's World of Mathematics, Polyrhomb [From Eric W. Weisstein, Apr 24 2009]

FORMULA

a(n) = 2*A006749(n) + A006746(n) + 2*A006748(n) + 2*A006747(n) + A056877(n) + 2*A056878(n) + A144553(n) + A142886(n). - Andrew Howroyd, Dec 04 2018

CROSSREFS

Cf. A000105, A056780, A057973, A151522.

Sequence in context: A132364 A110490 A132868 * A320735 A176697 A320736

Adjacent sequences:  A056780 A056781 A056782 * A056784 A056785 A056786

KEYWORD

nonn,hard,changed

AUTHOR

James A. Sellers, Aug 28 2000

EXTENSIONS

More terms from Don Reble, Nov 01 2001

a(15)-a(18) from Joseph Myers, Nov 15 2010

Offset corrected and a(19)-a(28) from Andrew Howroyd, Dec 04 2018

STATUS

approved

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Last modified December 9 14:42 EST 2018. Contains 318023 sequences. (Running on oeis4.)