OFFSET
1,3
COMMENTS
Row products of triangle A193829, if n >= 2. - Omar E. Pol, Aug 31 2011
When p is prime a(p) = p-1. - Michel Marcus, May 15 2014
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
Since positive divisors of 12 are 1, 2, 3, 4, 6 and 12, a(12) = (2-1) *(3-2) *(4-3) *(6-4) *(12-6) = 1 *1 *1 *2 *6 = 12.
MATHEMATICA
Times@@Differences[Divisors[#]]&/@Range[80] (* Harvey P. Dale, Apr 20 2011 *)
PROG
(Haskell)
a057449 = product . a193829_row -- Reinhard Zumkeller, Jun 23 2013
(PARI) a(n) = {my(d = divisors(n)); prod(i=1, #d-1, d[i+1] - d[i]); } \\ Michel Marcus, May 15 2014
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Leroy Quet, Sep 25 2000
STATUS
approved