OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,1,1,2).
FORMULA
a(n) = a(n-1) + a(n-2) + a(n-3) + 2*a(n-4);
a(n) = (Sum_{k=0..n} (2^(n-k+1)-1)*(-1)^k) - (Sum_{k=0..floor(n/2)} (2^(n-2*k)-1)*(-1)^k).
a(n) = A112030(n)/10 + (-1)^n/6 +2^(n+3)/15. - R. J. Mathar, Feb 06 2011
MATHEMATICA
CoefficientList[Series[1/((1 + x) (1 - 2 x) (1 + x^2)), {x, 0, 50}], x] (* Vladimir Joseph Stephan Orlovsky, Jun 20 2011 *)
LinearRecurrence[{1, 1, 1, 2}, {1, 1, 2, 4}, 50] (* Harvey P. Dale, Oct 22 2011 *)
PROG
(PARI) x='x+O('x^50); Vec(1/((1+x)*(1-2*x)*(1+x^2))) \\ G. C. Greubel, Sep 26 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jan 22 2006
STATUS
approved