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A187039
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Numbers that have equal counts of even and odd exponents of primes in their factorization.
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2
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1, 12, 18, 20, 28, 44, 45, 48, 50, 52, 63, 68, 72, 75, 76, 80, 92, 98, 99, 108, 112, 116, 117, 124, 147, 148, 153, 162, 164, 171, 172, 175, 176, 188, 192, 200, 207, 208, 212, 236, 242, 244, 245, 261, 268, 272, 275, 279, 284, 288, 292, 304, 316, 320, 325, 332
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OFFSET
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1,2
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LINKS
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Zak Seidov, Table of n, a(n) for n = 1..1000
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EXAMPLE
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108 = 2^2*3^3 has one even and one odd exponent in its factorization and therefore qualifies.
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MATHEMATICA
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Reap[Do[fi=FactorInteger[n]; la=Mod[Last/@fi, 2]; If[Count[la, 1]==Count[la, 0], Sow[n]] , {n, 1, 10000}]][[2, 1]] (* Zak Seidov, Mar 04 2011 *)
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PROG
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(MAGMA) IsA187039:=func< n | #[ a: a in P | IsEven(a) ] eq #[ a: a in P | IsOdd(a) ] where P is [ g[2]: g in F ] where F is Factorization(n) >; [ n: n in [1..500] | IsA187039(n) ]; // Klaus Brockhaus, Mar 04 2011
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CROSSREFS
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Sequence in context: A070011 A084679 A072588 * A072357 A054753 A098899
Adjacent sequences: A187036 A187037 A187038 * A187040 A187041 A187042
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KEYWORD
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nonn
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AUTHOR
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Vladimir Shevelev, Mar 02 2011
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STATUS
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approved
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