OFFSET
0,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..655
FORMULA
E.g.f.: exp(2*((1+x)^2 - 1)).
a(n) ~ 2^(n - 1/2) * n^(n/2) * exp(-1 + 2*sqrt(n) - n/2). - Vaclav Kotesovec, Oct 23 2017
a(n) = 4*a(n-1)+4*(n-1)*a(n-2). - Robert Israel, Jun 16 2020
MAPLE
f:= rectoproc({a(n)=4*a(n-1)+4*(n-1)*a(n-2), a(0)=1, a(1)=4}, a(n), remember):
map(f, [$0..30]); # Robert Israel, Jun 16 2020
MATHEMATICA
nmax = 20; CoefficientList[Series[E^(2*((1+x)^2 - 1)), {x, 0, nmax}], x] * Range[0, nmax]! (* Vaclav Kotesovec, Oct 23 2017 *)
PROG
(PARI) N=66; x='x+O('x^N); Vec(serlaplace(exp(2*((1+x)^2-1))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 23 2017
STATUS
approved