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A300912
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Numbers of the form prime(x)*prime(y) where x and y are relatively prime.
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18
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4, 6, 10, 14, 15, 22, 26, 33, 34, 35, 38, 46, 51, 55, 58, 62, 69, 74, 77, 82, 85, 86, 93, 94, 95, 106, 118, 119, 122, 123, 134, 141, 142, 143, 145, 146, 155, 158, 161, 166, 177, 178, 187, 194, 201, 202, 205, 206, 209, 214, 215, 217, 218, 219, 221, 226, 249
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OFFSET
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1,1
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LINKS
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Andrew Howroyd, Table of n, a(n) for n = 1..10000
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EXAMPLE
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The sequence of all relatively prime pairs (columns) begins:
1 1 1 1 2 1 1 2 1 3 1 1 2 3 1 1 2 1 4 1 3 1 2 1 3
1 2 3 4 3 5 6 5 7 4 8 9 7 5 10 11 9 12 5 13 7 14 11 15 8
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MATHEMATICA
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Select[Range[100], And[PrimeOmega[#]==2, GCD@@PrimePi/@If[#==1, {}, FactorInteger[#]][[All, 1]]==1]&]
With[{nn=40}, Join[{4}, Take[Prime[#[[1]]]Prime[#[[2]]]&/@Select[Subsets[ Range[ nn], {2}], CoprimeQ@@#&]//Union, Floor[Prime[nn]/2]]]] (* Harvey P. Dale, Jan 04 2021 *)
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PROG
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(PARI) ok(n)={my(f=factor(n)); bigomega(f)==2 && gcd(apply(primepi, f[, 1]))==1} \\ Andrew Howroyd, Oct 26 2018
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CROSSREFS
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Cf. A001358, A000837, A001221, A001222, A006881, A289508, A289509, A318990.
Sequence in context: A065073 A359157 A084997 * A175706 A110507 A224467
Adjacent sequences: A300909 A300910 A300911 * A300913 A300914 A300915
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KEYWORD
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nonn
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AUTHOR
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Gus Wiseman, Sep 06 2018
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STATUS
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approved
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