OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..10000
M. Baake and U. Grimm, Coordination sequences for root lattices and related graphs, arXiv:cond-mat/9706122, Zeit. f. Kristallographie, 212 (1997), 253-256.
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.
FORMULA
a(n) = 16*n*(2 - 3*n + 4*n^2), n >= 1;
G.f.: (1 + 44*x + 198*x^2 + 140*x^3 + x^4)/(1-x)^4 = 1 + 48*x*(x+1)*(3*x+1)/(x-1)^4.
MATHEMATICA
Join[{1}, Table[16n (2-3n+4n^2), {n, 30}]] (* Harvey P. Dale, Oct 21 2011 *)
PROG
(Magma) [1], [16*n*(2-3*n+4*n^2): n in [1..50]]; // Vincenzo Librandi, Oct 22 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
mbaake(AT)sunelc3.tphys.physik.uni-tuebingen.de (Michael Baake)
STATUS
approved