OFFSET
0,2
COMMENTS
a(n) modulo 2 is A131719(n+2).
FORMULA
G.f.: (1 - 5*x + 2*x^3 - 3*x^4 + 2*x^5 - x^6)/((1 + x)*(1 - x + x^2)^3).
a(3*k) = (-1)^k*(k + 1)*(2*k + 1).
a(3*k + 1) = -(-1)^k*(k + 1)*(2*k + 3).
a(3*k + 2) = -(-1)^k*(k + 3)^2.
MATHEMATICA
CoefficientList[Series[(1 - 5*x + 2*x^3 - 3*x^4 + 2*x^5 - x^6)/((1 + x)*(1 - x + x^2)^3) , {x, 0, 35}], x] (* Indranil Ghosh, Mar 08 2017 *)
PROG
(PARI) print(Vec((1 - 5*x + 2*x^3 - 3*x^4 + 2*x^5 - x^6)/((1 + x)*(1 - x + x^2)^3) + O(x^36))); \\ Indranil Ghosh, Mar 08 2017
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Paul Barry, Mar 07 2017
EXTENSIONS
More terms from Indranil Ghosh, Mar 08 2017
STATUS
approved