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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

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.

LINKS

Table of n, a(n) for n=0..14.

J. H. Conway and N. J. A. Sloane, Low-Dimensional Lattices VII: Coordination Sequences, Proc. Royal Soc. London, A453 (1997), 2369-2389 (pdf).

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

Adjacent sequences:  A035844 A035845 A035846 * A035848 A035849 A035850

KEYWORD

nonn,easy

AUTHOR

Joan Serra-Sagrista (jserra(AT)ccd.uab.es)

STATUS

approved

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Last modified October 28 07:43 EDT 2021. Contains 348321 sequences. (Running on oeis4.)