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A122179
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Number of ways to write n as n = x*y*z with 1<x<=y<=z<n.
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13
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0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 2, 0, 0, 1, 1, 0, 1, 0, 2, 0, 0, 0, 3, 0, 0, 0, 2, 0, 1, 0, 1, 1, 0, 0, 4, 0, 1, 0, 1, 0, 2, 0, 2, 0, 0, 0, 4, 0, 0, 1, 3, 0, 1, 0, 1, 0, 1, 0, 6, 0, 0, 1, 1, 0, 1, 0, 4, 1, 0, 0, 4, 0, 0, 0, 2, 0, 4, 0, 1, 0, 0, 0, 6, 0, 1, 1, 3, 0, 1, 0, 2, 1
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OFFSET
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1,24
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COMMENTS
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x,y,z are proper factors of n. a(n) > 0 iff n is a term of A033942; a(n) = 0 iff n is a term of A037143.
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LINKS
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EXAMPLE
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a(24) = 2 because 24 = 2*2*6 = 2*3*4, two products of three proper factors of 24.
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PROG
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(PARI) for(n=1, 105, t=0; for(x=2, n-1, for(y=x, n-1, for(z=y, n-1, if(x*y*z==n, t++)))); print1(t, ", "))
(PARI) A122179(n) = { my(s=0); fordiv(n, x, if((x>1)&&(x<n), for(y=x, n-1, for(z=y, n-1, if(x*y*z==n, s++))))); (s); }; \\ Antti Karttunen, Aug 24 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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