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A298267
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a(n) is the maximum number of heptiamonds in a hexagon of order n.
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1
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0, 3, 7, 13, 21, 30, 42, 54, 69, 85, 103, 123, 144, 168, 192, 219, 247, 277, 309, 342, 378, 414, 453, 493, 535, 579, 624, 672, 720, 771, 823, 877, 933, 990, 1050, 1110, 1173, 1237, 1303, 1371, 1440, 1512, 1584, 1659, 1735, 1813, 1893, 1974, 2058, 2142
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OFFSET
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0,2
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COMMENTS
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There are 24 heptiamonds.
It would be nice if this idea could be generalized to state that the hexagon can contain the maximum number of polyiamonds of any given size.
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LINKS
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FORMULA
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a(n) = floor((6*n^2)/7).
G.f.: x*(1 + x)*(3 - 2*x + 4*x^2 - 2*x^3 + 3*x^4) / ((1 - x)^3*(1 + x + x^2 + x^3 + x^4 + x^5 + x^6)).
a(n) = 2*a(n-1) - a(n-2) + a(n-7) - 2*a(n-8) + a(n-9) for n>8.
(End)
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MATHEMATICA
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CROSSREFS
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Cf. A033581 (The number of triangles in a hexagon), A291582 (hexiamond tiling).
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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