OFFSET
0,1
COMMENTS
Sequence extrapolated to n = 0 using recurrence.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..200
Eric Weisstein's World of Mathematics, Crossed Prism Graph
Eric Weisstein's World of Mathematics, Independent Vertex Set
Eric Weisstein's World of Mathematics, Vertex Cover
Index entries for linear recurrences with constant coefficients, signature (7, -7).
FORMULA
a(n) = 7*a(n-1) - 7*a(n-2) for n > 1.
G.f.: (2 - 7*x)/(1 - 7*x + 7*x^2).
MATHEMATICA
CoefficientList[Series[(2 - 7 x)/(1 - 7 x + 7 x^2), {x, 0, 22}], x] (* Michael De Vlieger, Aug 31 2017 *)
Table[(1/2 (7 - Sqrt[21]))^n + (1/2 (7 + Sqrt[21]))^n, {n, 0, 20}] // Expand (* Eric W. Weisstein, Sep 21 2017 *)
LinearRecurrence[{7, -7}, {7, 35}, {0, 20}] (* Eric W. Weisstein, Sep 21 2017 *)
PROG
(PARI) Vec((2 - 7*x)/(1 - 7*x + 7*x^2) + O(x^30))
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Aug 31 2017
STATUS
approved