OFFSET
0,2
REFERENCES
Inorganic Crystal Structure Database: Collection Code 24690.
LINKS
Colin Barker, 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 (2,-1,0,0,1,-2,1).
FORMULA
From N. J. A. Sloane, Mar 15 1996: (Start)
a(5*k) = 55*k^2 + 2 with k>0 and a(0)=1,
a(5*k+1) = 55*k^2 + 22*k + 4,
a(5*k+2) = 55*k^2 + 44*k + 10,
a(5*k+3) = 55*k^2 + 66*k + 21,
a(5*k+4) = 55*k^2 + 88*k + 37. (End)
G.f.: (1 + 2*x + 3*x^2 + 5*x^3 + 5*x^4 + 3*x^5 + 2*x^6 + x^7)/((1 - x)^3*(1 + x + x^2 + x^3 + x^4)). - Bruno Berselli, Jul 24 2013
a(n) = 2*a(n-1) - a(n-2) + a(n-5) - 2*a(n-6) + a(n-7) for n>7. - Colin Barker, Feb 15 2018
MATHEMATICA
LinearRecurrence[{2, -1, 0, 0, 1, -2, 1}, {1, 4, 10, 21, 37, 57, 81, 109}, 50] (* Harvey P. Dale, Jul 29 2015 *)
PROG
(PARI) Vec((1 + x)*(1 + x + 2*x^2 + 3*x^3 + 2*x^4 + x^5 + x^6) / ((1 - x)^3*(1 + x + x^2 + x^3 + x^4)) + O(x^60)) \\ Colin Barker, Feb 15 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved