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Search: id:A136567
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| A136567 |
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a(n) = number of exponents occurring only once each in the prime-factorization of n. |
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+0
2
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| 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 2, 1, 0, 0, 1, 1, 2, 1, 2, 0, 0, 1, 2, 1, 0, 1, 2, 1, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 2, 1, 0, 1, 2, 2, 0, 1, 2, 1, 2, 0, 2, 1, 2, 0, 2, 0, 0, 1, 1, 1, 0, 2, 1, 0, 0, 1, 2, 0, 0, 1, 2, 1, 0, 2, 2, 0, 0, 1, 2, 1, 0, 1, 1, 0, 0, 0, 2, 1, 1, 0, 2, 0, 0, 0, 2, 1, 2, 2, 0, 1, 0, 1, 2, 0
(list; graph; listen)
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OFFSET
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1,12
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COMMENT
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Records are in A006939: 1, 2, 12, 360, 75600, ..., . - Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 20 2008
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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4200 = 2^3 * 3^1 * 5^2 * 7^1. The exponents of the prime factorization are therefore 3,1,2,1. The exponents occurring exactly once are 2 and 3. So a(4200) = 2.
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MATHEMATICA
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f[n_] := Block[{fi = Sort[Last /@ FactorInteger@n]}, Count[ Count[fi, # ] & /@ Union@fi, 1]]; f[1] = 0; Array[f, 105] - Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 20 2008
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CROSSREFS
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Cf. A071625, A136566.
For a(n)=0 see A130092 plus the term 1; for a(n)=1 see A000961.
Sequence in context: A082858 A115953 A143379 this_sequence A109708 A035468 A051777
Adjacent sequences: A136564 A136565 A136566 this_sequence A136568 A136569 A136570
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet, Jan 07 2008
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 20 2008
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