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A135937
a(1)=1; for n>=2, a(n) = Product_{d|a(n-1)} (d+1), where the product is over all positive divisors d of a(n-1).
1
1, 2, 6, 168, 6623019333730800000
OFFSET
1,2
COMMENTS
The next term is a lot bigger than 70000! and is too large to include. - Stefan Steinerberger, Dec 31 2007
EXAMPLE
The positive divisors of a(3)=6 are 1,2,3,6. So a(4) = (1+1)*(2+1)*(3+1)*(6+1) = 2*3*4*7 = 168.
MATHEMATICA
a = {1}; Do[AppendTo[a, Times @@ (Divisors[a[[ -1]]] + 1)], {4}]; a (* Stefan Steinerberger, Dec 31 2007 *)
CROSSREFS
Cf. A135938.
Sequence in context: A329980 A199482 A168649 * A182523 A137532 A072116
KEYWORD
nonn
AUTHOR
Leroy Quet, Dec 07 2007
EXTENSIONS
a(5) from Stefan Steinerberger, Dec 31 2007
STATUS
approved