OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..281
FORMULA
a(n) = A162663(n,n).
MAPLE
b:= proc(n, k) option remember; `if`(n=0, 1, add(binomial(n-1, j-1)
*add(d^(j-1), d=numtheory[divisors](k))*b(n-j, k), j=1..n))
end:
a:= n-> b(n$2):
seq(a(n), n=0..18);
MATHEMATICA
b[n_, k_] := b[n, k] = If[n == 0, 1, Sum[Binomial[n - 1, j - 1] Sum[d^(j - 1), {d, Divisors[k]}] b[n - j, k], {j, 1, n}]];
a[n_] := b[n, n];
a /@ Range[0, 18] (* Jean-François Alcover, Dec 12 2020, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 17 2017
STATUS
approved