OFFSET
0,2
REFERENCES
Gmelin Handbook of Inorg. and Organomet. Chem., 8th Ed., 1994, TYPIX search code (225) cF12.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
R. W. Grosse-Kunstleve, Coordination Sequences and Encyclopedia of Integer Sequences
R. W. Grosse-Kunstleve, G. O. Brunner and N. J. A. Sloane, Algebraic Description of Coordination Sequences and Exact Topological Densities for Zeolites, Acta Cryst., A52 (1996), pp. 879-889.
Sean A. Irvine, Generating Functions for Coordination Sequences of Zeolites, after Grosse-Kunstleve, Brunner, and Sloane
Index entries for linear recurrences with constant coefficients, signature (0,3,0,-3,0,1).
FORMULA
G.f.: (1+4*x+19*x^2+12*x^3+19*x^4+4*x^5+x^6) / ((1-x)^3*(1+x)^3). - Colin Barker, Dec 12 2012
From Colin Barker, Jan 27 2016: (Start)
a(n) = (5*(-1)^n*n^2+15*n^2+(-1)^n+7)/4 for n>0.
a(n) = 5*n^2+2 for n>0 and even.
a(n) = (5*n^2+3)/2 for n odd.
(End)
MATHEMATICA
CoefficientList[Series[-(x^6 + 4 x^5 + 19 x^4 + 12 x^3 + 19 x^2 + 4 x + 1)/((x - 1)^3 (x + 1)^3), {x, 0, 50}], x] (* Vincenzo Librandi, Oct 15 2013 *)
PROG
(PARI) Vec((1+4*x+19*x^2+12*x^3+19*x^4+4*x^5+x^6)/((1-x)^3*(1+x)^3) + O(x^100)) \\ Colin Barker, Jan 27 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved