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 A056783 Number of diamond polyominoes with n cells. 4
 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 John Mason, Table of n, a(n) for n = 1..50 Ed Pegg, Jr., Illustrations of polyforms. M. Keller, Counting Polyforms. M. Vicher, Polyforms. Eric Weisstein's World of Mathematics, Polyrhomb. 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: A132868 A357792 A361625 * A320735 A176697 A320736 Adjacent sequences: A056780 A056781 A056782 * A056784 A056785 A056786 KEYWORD nonn,hard 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 June 3 18:04 EDT 2023. Contains 363116 sequences. (Running on oeis4.)