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A008389
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Coordination sequence for A_7 lattice.
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2
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1, 56, 812, 5768, 26474, 91112, 256508, 623576, 1356194, 2703512, 5025692, 8823080, 14768810, 23744840, 36881420, 55599992, 81659522, 117206264, 164826956, 227605448, 309182762, 413820584
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OFFSET
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0,2
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REFERENCES
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R. Bacher, P. de la Harpe and B. Venkov, Series de croissance et series d'Ehrhart associees aux reseaux de racines, C. R. Acad. Sci. Paris, 325 (Series 1) (1997), 1137-1142.
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..1000
J. H. Conway and N. J. A. Sloane, Low-Dimensional Lattices VII: Coordination Sequences, Proc. Royal Soc. London, A453 (1997), 2369-2389 (Abstract, pdf, ps).
Index to sequences with linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).
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FORMULA
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G.f.: -(x+1)*(x^6+48*x^5+393*x^4+832*x^3+393*x^2+48*x+1)/(x-1)^7. [Colin Barker, Sep 26 2012]
a(n) = 2+n^2*(143*n^4+770*n^2+707)/30 with n>0, a(0)=1. [Bruno Berselli, Sep 26 2012]
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MAPLE
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143/30*n^6+77/3*n^4+707/30*n^2+2;
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CROSSREFS
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Sequence in context: A105940 A175602 A182866 * A219937 A008921 A114059
Adjacent sequences: A008386 A008387 A008388 * A008390 A008391 A008392
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane and J. H. Conway (conway(AT)math.princeton.edu)
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STATUS
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approved
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