OFFSET
0,4
FORMULA
E.g.f.: log(1 + Sum_{k>=1} k^(k-2)*x^k/k!).
a(n) ~ 2 * n^(n-2) / 3. - Vaclav Kotesovec, Jan 24 2019
MAPLE
seq(n!*coeff(series(log(1-LambertW(-x)*(2+LambertW(-x))/2), x=0, 22), x, n), n=0..21); # Paolo P. Lava, Jan 28 2019
MATHEMATICA
nmax = 21; CoefficientList[Series[Log[1 - LambertW[-x] (2 + LambertW[-x])/2], {x, 0, nmax}], x] Range[0, nmax]!
a[n_] := a[n] = n^(n - 2) - Sum[Binomial[n, k] (n - k)^(n - k - 2) k a[k], {k, 1, n - 1}]/n; a[0] = 0; Table[a[n], {n, 0, 21}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jan 23 2019
STATUS
approved