OFFSET
1,1
COMMENTS
If a number is in the sequence, all of its multiples also meet the criterion, but are not included. This is what the word "primitive" refers to.
FORMULA
a(n) appears to be asymptotic to c*n with 12 < c < 15. - Benoit Cloitre, Sep 16 2002
EXAMPLE
The product of the factorials of the proper divisors of 24, 1! * 2! * 3! * 4! * 6! * 8! * 12!, is divisible by 2^26 and therefore does not divide 24! (which is divisible by 2^22 only). 24 is the smallest number with this property. - M. F. Hasler, Dec 31 2016
MATHEMATICA
f[n_] := n!/Apply[Times, Drop[Divisors[n], -1]! ]; a = {}; Do[b = f[n]; If[ !IntegerQ[b], If[ Select[n/a, IntegerQ] == {}, a = Append[a, n]]], {n, 1, 725}]; a
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v & Amarnath Murthy, Sep 14 2002
EXTENSIONS
Edited by M. F. Hasler, Dec 30 2016
STATUS
approved