A035847 Coordination sequence for A_21 lattice.

1, 462, 53592, 2798642, 83945862, 1657762722, 23539760552, 255689552382, 2224042468032, 16045139112002, 98698280879352, 529244674992222, 2518877938240202, 10799525727846702, 42229092648830472

Offset

0,2

Links

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

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

Adjacent sequences: A035844 A035845 A035846 * A035848 A035849 A035850

Keyword

nonn,easy

Author

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

Status

approved