OFFSET
1,2
COMMENTS
Number of nonempty subsets of divisors of n = A100587(n).
FORMULA
a(2^n) = (2^(n+1) - 1)!.
EXAMPLE
For n = 2^2 = 4; divisors of 4: {1, 2, 4}; nonempty subsets of divisors of n: {1}, {2}, {4}, {1, 2}, {1, 4}, {2, 4}, {1, 2, 4}; product of sums of elements of subsets = 1*2*4*3*5*6*7 = 5040 = (2^3 - 1)! = 7!.
MATHEMATICA
Table[Times@@(Total/@Rest[Subsets[Divisors[n]]]), {n, 20}] (* Harvey P. Dale, Jan 22 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Sep 20 2013
STATUS
approved