OFFSET
0,3
COMMENTS
Invert transform of A001515, shifted right one place.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..405
N. J. A. Sloane, Transforms
FORMULA
a(n) ~ 2^(n - 1/2) * n^(n-1) / exp(n-1). - Vaclav Kotesovec, Sep 18 2021
MAPLE
b:= proc(n) option remember;
`if`(n<2, n+1, (2*n-1)*b(n-1)+b(n-2))
end:
a:= proc(n) option remember;
`if`(n=0, 1, add(b(j-1)*a(n-j), j=1..n))
end:
seq(a(n), n=0..30); # Alois P. Heinz, Jan 11 2023
MATHEMATICA
nmax = 21; CoefficientList[Series[1/(1 - x/(1 - x + ContinuedFractionK[-k x, 1 - x, {k, 1, nmax}])), {x, 0, nmax}], x]
nmax = 21; CoefficientList[Series[1/(1 - Sum[HypergeometricPFQ[{k, 1 - k}, {}, -1/2] x^k, {k, 1, nmax}]), {x, 0, nmax}], x]
a[0] = 1; a[n_] := a[n] = Sum[HypergeometricPFQ[{k, 1 - k}, {}, -1/2] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 21}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jun 04 2018
STATUS
approved