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URL: https://oeis.org/A052922

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A052922
Expansion of 1/(1 - 2*x^3 - x^4).
2
1, 0, 0, 2, 1, 0, 4, 4, 1, 8, 12, 6, 17, 32, 24, 40, 81, 80, 104, 202, 241, 288, 508, 684, 817, 1304, 1876, 2318, 3425, 5056, 6512, 9168, 13537, 18080, 24848, 36242, 49697, 67776, 97332, 135636, 185249, 262440, 368604, 506134, 710129, 999648, 1380872
OFFSET
0,4
FORMULA
G.f.: 1/(1 - 2*x^3 - x^4).
a(n) = 2*a(n-3) + a(n-4), with a(0)=1, a(1)=0, a(2)=0, a(3)=2.
a(n) = Sum_{alpha=RootOf(-1+2*z^3+z^4)} (1/86)*(4 +26*alpha -3*alpha^2 -6*alpha^3)*alpha^(-1-n).
MAPLE
spec := [S, {S=Sequence(Prod(Z, Z, Union(Z, Z, Prod(Z, Z))))}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..50);
seq(coeff(series(1/(1 -2*x^3 -x^4), x, n+1), x, n), n = 0..50); # G. C. Greubel, Oct 16 2019
# Alternative:
A052922 := proc(n)
if n <=3 then
op(n+1, [1, 0, 0, 2]) ;
else
2*procname(n-3)+procname(n-4) ;
end if;
end proc:
seq(A052922(n), n=0..30) ; # R. J. Mathar, Nov 22 2024
MATHEMATICA
LinearRecurrence[{0, 0, 2, 1}, {1, 0, 0, 2}, 50] (* G. C. Greubel, Oct 16 2019 *)
CoefficientList[Series[1/(1-2x^3-x^4), {x, 0, 50}], x] (* Harvey P. Dale, Nov 04 2024 *)
PROG
(PARI) my(x='x+O('x^50)); Vec(1/(1 -2*x^3 -x^4)) \\ G. C. Greubel, Oct 16 2019
(Magma) R<x>:=PowerSeriesRing(Integers(), 50); Coefficients(R!( 1/(1 -2*x^3 -x^4) )); // G. C. Greubel, Oct 16 2019
(SageMath)
def A052922_list(prec):
P.<x> = PowerSeriesRing(ZZ, prec)
return P(1/(1 -2*x^3 -x^4)).list()
A052922_list(50) # G. C. Greubel, Oct 16 2019
(GAP) a:=[1, 0, 0, 2];; for n in [5..50] do a[n]:=2*a[n-3]+a[n-4]; od; a; # G. C. Greubel, Oct 16 2019
CROSSREFS
Cf. A117413 (bijection).
Sequence in context: A158454 A049243 A077908 * A181930 A256797 A109167
KEYWORD
easy,nonn
EXTENSIONS
More terms from James Sellers, Jun 05 2000
STATUS
approved