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A081060 Product of differences of distinct prime factors of n. 2
1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 2, 1, 1, 1, 1, 3, 4, 9, 1, 1, 1, 11, 1, 5, 1, 6, 1, 1, 8, 15, 2, 1, 1, 17, 10, 3, 1, 20, 1, 9, 2, 21, 1, 1, 1, 3, 14, 11, 1, 1, 6, 5, 16, 27, 1, 6, 1, 29, 4, 1, 8, 72, 1, 15, 20, 30, 1, 1, 1, 35, 2, 17, 4, 110, 1, 3, 1, 39, 1, 20, 12, 41, 26, 9, 1, 6, 6, 21, 28 (list; graph; refs; listen; history; internal format)
OFFSET

1,10

COMMENTS

a(n)=1 iff n is 3-smooth (A003586) or n is a prime power (A000961), see A081061;

a(A006881(k))>1 for k>1; if a(n)>1 then A079275(n)>0.

FORMULA

a(n) = Product(abs(p-q): p, q distinct prime factors of n).

EXAMPLE

a(42) = a(2*3*7) = |2-3|*|2-7|*|3-7| = 1*5*4 = 20.

CROSSREFS

Sequence in context: A119288 A028234 A052125 * A131268 A109221 A046643

Adjacent sequences:  A081057 A081058 A081059 * A081061 A081062 A081063

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 04 2003

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Last modified February 14 20:38 EST 2012. Contains 205663 sequences.