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%I #15 Jul 01 2018 12:14:38
%S 1,2550,1626900,462400850,74214929700,7664751475110,553532399900300,
%T 29615721096973650,1225039098412340850,40483994261907371450,
%U 1097141899359944015580,24907942311608525171550,482175421833854221370900
%N Coordination sequence for A_50 lattice.
%H R. Bacher, P. de la Harpe and B. Venkov, <a href="https://doi.org/10.1016/S0764-4442(97)83542-2">Séries de croissance et séries d'Ehrhart associées aux réseaux de racines</a>, C. R. Acad. Sci. Paris, 325 (Series 1) (1997), 1137-1142.
%H J. H. Conway and N. J. A. Sloane, Low-Dimensional Lattices VII: Coordination Sequences, Proc. Royal Soc. London, A453 (1997), 2369-2389 (<a href="http://neilsloane.com/doc/Me220.pdf">pdf</a>).
%H Joan Serra-Sagrista, <a href="http://dx.doi.org/10.1016/S0020-0190(00)00119-8">Enumeration of lattice points in l_1 norm</a>, Inf. Proc. Lett. 76 (1-2) (2000) 39-44.
%H <a href="/index/Rec#order_50">Index entries for linear recurrences with constant coefficients</a>, signature (50, -1225, 19600, -230300, 2118760, -15890700, 99884400, -536878650, 2505433700, -10272278170, 37353738800, -121399651100, 354860518600, -937845656300, 2250829575120, -4923689695575, 9847379391150, -18053528883775, 30405943383200, -47129212243960, 67327446062800, -88749815264600, 108043253365600, -121548660036300, 126410606437752, -121548660036300, 108043253365600, -88749815264600, 67327446062800, -47129212243960, 30405943383200, -18053528883775, 9847379391150, -4923689695575, 2250829575120, -937845656300, 354860518600, -121399651100, 37353738800, -10272278170, 2505433700, -536878650, 99884400, -15890700, 2118760, -230300, 19600, -1225, 50, -1).
%F Sum_{d=1..50} C(51, d)*C(m/2-1, d-1)*C(50-d+m/2, m/2), where norm m is always even.
%K nonn,easy
%O 0,2
%A Joan Serra-Sagrista (jserra(AT)ccd.uab.es)
%E a(9)-a(10) corrected, a(11)-a(12) added by _Ray Chandler_, Jan 19 2016
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