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URL: https://oeis.org/A004701

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A004701
Expansion of e.g.f. 1/(4 - exp(x) - exp(2*x) - exp(3*x)).
6
1, 6, 86, 1836, 52250, 1858716, 79345346, 3951633636, 224917803770, 14402023566156, 1024662142371506, 80191908540219636, 6846505625682597290, 633241684193651067996, 63074628985206471485666, 6731364953866743063784836
OFFSET
0,2
LINKS
FORMULA
a(0) = 1; a(n) = Sum_{k=1..n} binomial(n,k) * (1 + 2^k + 3^k) * a(n-k). - Ilya Gutkovskiy, Jan 15 2020
MAPLE
seq(coeff(series(factorial(n)*(4-exp(x)-exp(2*x)-exp(3*x))^(-1), x, n+1), x, n), n = 0 .. 15); # Muniru A Asiru, Oct 10 2018
MATHEMATICA
With[{nn=20}, CoefficientList[Series[1/(4-Exp[x]-Exp[2*x]-Exp[3*x]), {x, 0, nn}], x] Range[0, nn]!] (* Vincenzo Librandi, Jun 14 2012 *)
PROG
(PARI) x='x+O('x^30); Vec(serlaplace(1/(4-sum(k=1, 3, exp(k*x))))) \\ G. C. Greubel, Oct 09 2018
(Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(1/(4-Exp(x)-Exp(2*x)-Exp(3*x)))); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, Oct 09 2018
CROSSREFS
Column k=3 of A320253.
Sequence in context: A155654 A231165 A091881 * A177570 A343636 A369624
KEYWORD
nonn
STATUS
approved