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A010006
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Coordination sequence for C_3 lattice.
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6
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1, 18, 66, 146, 258, 402, 578, 786, 1026, 1298, 1602, 1938, 2306, 2706, 3138, 3602, 4098, 4626, 5186, 5778, 6402, 7058, 7746, 8466, 9218, 10002, 10818, 11666, 12546, 13458, 14402, 15378, 16386, 17426
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| If Y_i (i=1,2,3) are 2-blocks of a (2n+1)-set X then a(n-1) is the number of 5-subsets of X intersecting each Y_i (i=1,2,3). - Milan R. Janjic (agnus(AT)blic.net), Oct 28 2007
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REFERENCES
| 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.
J. Serra-Sagrista, Enumeration of lattice points in l_1 norm, Information Processing Letters, 76, no. 1-2 (2000), 39-44.
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LINKS
| Milan Janjic, Two Enumerative Functions
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FORMULA
| a(0)=1, a(n)=16*n^2 + 2, n >= 1; G.f.: (1+15*x+15*x^2+x^3)/(1-x)^3.
G.f. for coordination sequence of C_n lattice: Sum(binomial(2*n, 2*i)*z^i, i=0..n)/(1-z)^n.
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CROSSREFS
| Cf. A206399.
Sequence in context: A090073 A016728 A165029 * A044156 A044537 A143859
Adjacent sequences: A010003 A010004 A010005 * A010007 A010008 A010009
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KEYWORD
| nonn,changed
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), mbaake(AT)sunelc3.tphys.physik.uni-tuebingen.de (Michael Baake)
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