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Number of ways n can be properly factored.
27

%I #11 Oct 12 2018 21:58:32

%S 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,

%T 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,

%U 3,1,4,0,15,0,1,3,3,1,4,0,11,4,1,0,10,1,1,1,6,0,10

%N Number of ways n can be properly factored.

%C 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

%H Reinhard Zumkeller, <a href="/A028422/b028422.txt">Table of n, a(n) for n = 1..10000</a>

%e 12 can be expressed as 2*6, 3*4 or 2*2*3, so a(12)=3.

%o (Haskell)

%o a028422 1 = 0

%o a028422 n = (map (last . init) a066032_tabl) !! (n-1)

%o -- _Reinhard Zumkeller_, Oct 01 2012

%Y A001055(n) - 1.

%Y Cf. A216599, A216600, A216601, A216602.

%K nonn

%O 1,8

%A Glen Burch (gburch(AT)erols.com)