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 A187039 Numbers that have equal counts of even and odd exponents of primes in their factorization. 2
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Zak Seidov, Table of n, a(n) for n = 1..1000 EXAMPLE 108 = 2^2*3^3 has one even and one odd exponent in its factorization and therefore qualifies. MATHEMATICA 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 *) PROG (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 CROSSREFS Sequence in context: A070011 A084679 A072588 * A072357 A054753 A098899 Adjacent sequences:  A187036 A187037 A187038 * A187040 A187041 A187042 KEYWORD nonn AUTHOR Vladimir Shevelev, Mar 02 2011 STATUS approved

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