OFFSET
0,1
COMMENTS
a(n) is the convolution of S(n) with the sequence (1,0,-1,0,1,0,-1,0,....) A056594.
LINKS
Index entries for linear recurrences with constant coefficients, signature (1, 0, 2, 2, 1, 1).
FORMULA
a(n)=a(n-1)+2a(n-3)+2a(n-4)+a(n-5)+a(n-6), a(0)=4, a(1)=1, a(2)=-1, a(3)=6, a(4)=16, a(5)=20. G.f.: (4 - 3*x - 2*x^2 - x^3)/(1 - x - 2*x^3 - 2*x^4 - x^5 - x^6).
MATHEMATICA
CoefficientList[Series[(4 - 3*x - 2*x^2 - x^3)/(1 - x - 2*x^3 - 2*x^4 - x^5 - x^6), {x, 0, 40}], x]
LinearRecurrence[{1, 0, 2, 2, 1, 1}, {4, 1, -1, 6, 16, 20}, 40] (* Harvey P. Dale, Mar 09 2013 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Mario Catalani (mario.catalani(AT)unito.it), Sep 01 2002
STATUS
approved