OFFSET
0,2
FORMULA
E.g.f.: exp(2*x) * BesselI(0,2*x) / (1 - x).
a(n) ~ exp(2) * BesselI(0,2) * n!. - Vaclav Kotesovec, Nov 20 2021
MATHEMATICA
Table[n! Sum[(2 k)!/(k!)^3, {k, 0, n}], {n, 0, 21}]
nmax = 21; CoefficientList[Series[Exp[2 x] BesselI[0, 2 x]/(1 - x), {x, 0, nmax}], x] Range[0, nmax]!
PROG
(PARI) a(n) = n! * sum(k=0, n, (2*k)! / (k!)^3) \\ Andrew Howroyd, Nov 20 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Nov 20 2021
STATUS
approved