OFFSET
0,3
FORMULA
a(n) ~ (n!)^n.
a(n) ~ 2^(n/2) * Pi^(n/2) * n^(n*(2*n+1)/2) / exp(n^2-1/12).
MAPLE
with(NumberTheory): seq(product(sigma[n](k), k = 1..n), n = 0..10);
MATHEMATICA
Table[Product[DivisorSigma[n, k], {k, 1, n}], {n, 1, 10}]
PROG
(PARI) a(n) = prod(k=1, n, sigma(k, n));
for(n=1, 10, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Aug 20 2019
EXTENSIONS
a(0)=1 prepended by Alois P. Heinz, Aug 23 2019
STATUS
approved