OFFSET
1,2
COMMENTS
Logarithmic derivative of A006882.
FORMULA
L.g.f.: log(Sum_{k>=0} k!! * x^k).
MATHEMATICA
a[n_] := a[n] = n n!! - Sum[k!! a[n - k], {k, 1, n - 1}]; Table[a[n], {n, 1, 26}]
nmax = 26; CoefficientList[Series[Log[Sum[k!! x^k, {k, 0, nmax}]], {x, 0, nmax}], x] Range[0, nmax] // Rest
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Dec 14 2019
STATUS
approved