OFFSET
1,2
FORMULA
a(n) = Sum_{k=1..n} binomial(sigma(k) + n - k - 1, n - k).
EXAMPLE
The a(5) = 12 multisets of divisors:
{1,1,1,1} {1,1,1} {1,1} {1} {}
{1,1,2} {1,3} {2}
{1,2,2} {3,3} {4}
{2,2,2}
MATHEMATICA
multchoo[n_, k_]:=Binomial[n+k-1, k];
Table[Sum[multchoo[DivisorSigma[0, k], n-k], {k, n}], {n, 10}]
CROSSREFS
Antidiagonal sums of the array A343658 (or row sums of the triangle).
Dominates A343657.
A000005 counts divisors.
A007318 counts k-sets of elements of {1..n}.
A059481 counts k-multisets of elements of {1..n}.
A343656 counts divisors of powers.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Apr 30 2021
STATUS
approved