OFFSET
0,1
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2,3,-4,-2)
FORMULA
G.f.: (x-2)*(2*x-1)*(1+x) / ( (2*x^2-1)*(x^2+2*x-1) ).
E.g.f.: cosh(sqrt(2)*x)*(1+exp(x)).
a(n) = ((sqrt(2))^n + (-sqrt(2))^n + (1+sqrt(2))^n + (1-sqrt(2))^n)/2.
a(0)=2, a(1)=1, a(2)=5, a(3)=7, a(n) = 2*a(n-1) + 3*a(n-2) - 4*a(n-3) - 2*a(n-4). - Harvey P. Dale, Jul 31 2012
MATHEMATICA
With[{nn=30}, CoefficientList[Series[Cosh[Sqrt[2]x](1+Exp[x]), {x, 0, nn}], x]Range[0, nn]!] (* or *) LinearRecurrence[{2, 3, -4, -2}, {2, 1, 5, 7}, 30] (* Harvey P. Dale, Jul 31 2012 *)
PROG
(PARI) x='x+O('x^50); Vec((x-2)*(2*x-1)*(1+x)/((2*x^2-1)*(x^2+2*x-1))) \\ G. C. Greubel, Aug 16 2018
(Magma) m:=50; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!((x-2)*(2*x-1)*(1+x)/((2*x^2-1)*(x^2+2*x-1)))); // G. C. Greubel, Aug 16 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 18 2003
STATUS
approved