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A035847 Coordination sequence for A_21 lattice. 0
1, 462, 53592, 2798642, 83945862, 1657762722, 23539760552, 255689552382, 2224042468032, 16045139112002, 98698280879352, 529244674992222, 2518877938240202, 10799525727846702, 42229092648830472 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
R. Bacher, P. de la Harpe and B. Venkov, Séries de croissance et séries d'Ehrhart associées aux réseaux de racines, C. R. Acad. Sci. Paris, 325 (Series 1) (1997), 1137-1142.
J. H. Conway and N. J. A. Sloane, Low-Dimensional Lattices VII: Coordination Sequences, Proc. Royal Soc. London, A453 (1997), 2369-2389 (pdf).
Joan Serra-Sagrista, Enumeration of lattice points in l_1 norm, Inf. Proc. Lett. 76 (1-2) (2000) 39-44.
Index entries for linear recurrences with constant coefficients, signature (21, -210, 1330, -5985, 20349, -54264, 116280, -203490, 293930, -352716, 352716, -293930, 203490, -116280, 54264, -20349, 5985, -1330, 210, -21, 1).
FORMULA
Sum_{d=1..21} C(22, d)*C(m/2-1, d-1)*C(21-d+m/2, m/2), where norm m is always even.
CROSSREFS
Sequence in context: A289349 A023912 A027565 * A140905 A208619 A318266
KEYWORD
nonn,easy
AUTHOR
Joan Serra-Sagrista (jserra(AT)ccd.uab.es)
STATUS
approved

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Last modified May 29 00:29 EDT 2024. Contains 372921 sequences. (Running on oeis4.)