OFFSET
0,14
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,-1,1,-1,2,-2,2,-1).
FORMULA
G.f.: 1 / ((1 - x) * (1 - x + x^2) * (1 + x^2) * (1 + x - x^3)).
a(n) = a(n+1) + a(n+5) - mod(floor((n-1)/2), 2) for all n in Z.
a(n) = -A247907(-8-n) for all n in Z.
EXAMPLE
G.f. = 1 + x + x^5 + x^6 + x^8 + x^11 + 2*x^13 - x^15 + 2*x^16 - x^17 + ...
MATHEMATICA
CoefficientList[Series[(1+x)/((1-x^4)(1+x^4-x^5)), {x, 0, 100}], x] (* Vincenzo Librandi, Sep 27 2014 *)
PROG
(PARI) {a(n) = if( n<0, n=-8-n; polcoeff( -1/((1-x)*(1-x+x^2)*(1+x^2)*(1 - x^2 - x^3)) + x * O(x^n), n), polcoeff( 1/((1-x)*(1-x+x^2)*(1+x^2)*(1+x-x^3)) + x * O(x^n), n))};
(Magma) R<x>:=PowerSeriesRing(Integers(), 70); Coefficients(R!((1 + x)/((1-x^4)*(1+x^4-x^5)))); // G. C. Greubel, Aug 04 2018
(SageMath)
def A247918_list(prec):
P.<x> = PowerSeriesRing(ZZ, prec)
return P( (1+x)/((1-x^4)*(1+x^4-x^5)) ).list()
A247918_list(70) # G. C. Greubel, Aug 08 2022
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Michael Somos, Sep 26 2014
STATUS
approved