OFFSET
0,3
FORMULA
a(n) ~ c * n!, where c = A065446 = 1/A048651 = 1/QPochhammer[1/2] = 3.4627466194550636115379573429244311645407579... - Vaclav Kotesovec, Mar 18 2019
MATHEMATICA
nmax = 22; CoefficientList[Series[Product[1/(1 - x^2^k/2^k), {k, 0, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
nmax = 22; CoefficientList[Series[Exp[Sum[Sum[Boole[IntegerQ[Log[2, d]]] d^(1 - k/d), {d, Divisors[k]}] x^k/k, {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
a[n_] := a[n] = If[n == 0, 1, (n - 1)! Sum[Sum[Boole[IntegerQ[Log[2, d]]] d^(1 - k/d), {d, Divisors[k]}] a[n - k]/(n - k)!, {k, 1, n}]]; Table[a[n], {n, 0, 22}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Mar 17 2019
STATUS
approved