OFFSET
0,2
REFERENCES
Jean-Guillaume Eon (jgeon(AT)iq.ufrj.br), personal communication, Jan 05, 2002.
LINKS
Jean-Guillaume Eon, Algebraic determination of generating functions for coordination sequences in crystal structures, Acta Cryst. A58 (2002), 47-53.
FORMULA
G.f.: (1+6*x+x^2)*(1+x^2)^2/(1-x^2)^3.
a(n) = 1 if n=1 or 2*n^2+5/2-(-1)^n*(n^2+1/2) if n>1. - C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 13 2004
MAPLE
1, seq(2*n^2+5/2-(-1)^n*(n^2+1/2), n=1..55); with(genfunc): seq(rgf_term((1+6*x+x^2)*(1+x^2)^2/(1-x^2)^3, x, i), i=0..55); # C. Ronaldo
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 19 2002
STATUS
approved