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A069625
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Number of distinct numbers that can be formed as a product of two or more divisors of n.
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0
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0, 1, 1, 3, 1, 6, 1, 6, 3, 6, 1, 19, 1, 6, 6, 10, 1, 19, 1, 19, 6, 6, 1, 44, 3, 6, 6, 19, 1, 58, 1, 15, 6, 6, 6, 65, 1, 6, 6, 44, 1, 58, 1, 19, 19, 6, 1, 85, 3, 19, 6, 19, 1, 44, 6, 44, 6, 6, 1, 268, 1, 6, 19, 21, 6, 58, 1, 19, 6, 58, 1, 156, 1, 6, 19, 19, 6, 58, 1, 85, 10, 6, 1, 268, 6, 6, 6, 44
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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COMMENTS
| a(p) = 1, a(p*q) = 6, a(p^2*q) = 19, a(p^4)= 10 etc. where p and q are primes. Question: To find an expression for a(N) where N = p^a*q^b*r^c...p,q,r are primes.
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EXAMPLE
| a(6) = 6 as the divisors of 6 are 1,2,3 and 6 and the distinct products of these divisors are 2,3,6,12,18 and 36.
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CROSSREFS
| Sequence in context: A019570 A040011 A066446 * A111614 A193279 A076889
Adjacent sequences: A069622 A069623 A069624 * A069626 A069627 A069628
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KEYWORD
| nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 27 2002
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EXTENSIONS
| Corrected and extended by David Wasserman (wasserma(AT)spawar.navy.mil), Apr 23 2003
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