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A035846 Coordination sequence for A_20 lattice. 0
1, 420, 44310, 2107140, 57671880, 1041949020, 13577591370, 135798494460, 1091481669390, 7302195414780, 41800229045610, 209294745286620, 933146517188760, 3759426449644740, 13853429338548630, 47171740235162340 (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..15.

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 (20, -190, 1140, -4845, 15504, -38760, 77520, -125970, 167960, -184756, 167960, -125970, 77520, -38760, 15504, -4845, 1140, -190, 20, -1).

FORMULA

Sum_{d=1..20} C(21, d)*C(m/2-1, d-1)*C(20-d+m/2, m/2), where norm m is always even.

CROSSREFS

Sequence in context: A023911 A135340 A135380 * A223941 A046167 A059951

Adjacent sequences:  A035843 A035844 A035845 * A035847 A035848 A035849

KEYWORD

nonn,easy

AUTHOR

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

STATUS

approved

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Last modified October 19 03:10 EDT 2021. Contains 348073 sequences. (Running on oeis4.)