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A035758
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Coordination sequence for C_21 lattice.
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0
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1, 882, 130242, 7796978, 255582978, 5369283570, 79749022402, 895903147122, 7996359740418, 58861356563058, 367891005738690, 1998142759241202, 9609441659124482, 41553956372047602, 163646115158499522
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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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
| 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).
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FORMULA
| ((1+x)/(1-x))^21 if norm is even; otherwise 0.
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CROSSREFS
| Sequence in context: A137064 A092675 A135127 * A107554 A089519 A206977
Adjacent sequences: A035755 A035756 A035757 * A035759 A035760 A035761
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KEYWORD
| nonn,easy
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AUTHOR
| Serra-Sagrista, Joan; jserra(AT)ccd.uab.es
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EXTENSIONS
| Recomputed Nov 25 1998 by N. J. A. Sloane (njas(AT)research.att.com).
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