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A028422
Number of ways n can be properly factored.
27
0, 0, 0, 1, 0, 1, 0, 2, 1, 1, 0, 3, 0, 1, 1, 4, 0, 3, 0, 3, 1, 1, 0, 6, 1, 1, 2, 3, 0, 4, 0, 6, 1, 1, 1, 8, 0, 1, 1, 6, 0, 4, 0, 3, 3, 1, 0, 11, 1, 3, 1, 3, 0, 6, 1, 6, 1, 1, 0, 10, 0, 1, 3, 10, 1, 4, 0, 3, 1, 4, 0, 15, 0, 1, 3, 3, 1, 4, 0, 11, 4, 1, 0, 10, 1, 1, 1, 6, 0, 10
OFFSET
1,8
COMMENTS
a(n) = A066032(n,n-1) for n > 1; also number of ways to write n as a product with all factors <= n/2. - Reinhard Zumkeller, Oct 01 2012
LINKS
EXAMPLE
12 can be expressed as 2*6, 3*4 or 2*2*3, so a(12)=3.
PROG
(Haskell)
a028422 1 = 0
a028422 n = (map (last . init) a066032_tabl) !! (n-1)
-- Reinhard Zumkeller, Oct 01 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Glen Burch (gburch(AT)erols.com)
STATUS
approved