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A122824
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Prime(semiprime(n)) - semiprime(prime(n)). Commutator [A000040,A001358] at n.
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12
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1, 4, 9, 8, 10, 12, 24, 24, 32, 15, 46, 24, 27, 34, 25, 40, 44, 46, 51, 54, 53, 46, 54, 60, 70, 70, 98, 105, 104, 91, 64, 72, 45, 48, 95, 118, 120, 120, 116, 108, 100, 96, 101, 118, 102, 144, 123, 86, 76, 81, 136, 138, 143, 112, 132, 131, 153, 160, 171, 169
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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a(1) = prime(semiprime(1)) - semiprime(prime(1)) = prime(4) - semiprime(2) = 7 - 6 = 1.
a(2) = prime(semiprime(2)) - semiprime(prime(2)) = prime(6) - semiprime(3) = 13 - 9 = 4.
a(3) = prime(semiprime(3)) - semiprime(prime(3)) = prime(9) - semiprime(5) = 23 - 14 = 9.
a(4) = prime(semiprime(4)) - semiprime(prime(4)) = prime(10) - semiprime(7) = 29 - 21 = 8.
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MATHEMATICA
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sp = Select[Range[1000], PrimeOmega[#] == 2 &]; Table[ Prime[ sp[[i]]] - sp[[Prime[i]]], {i, PrimePi@ Length@ sp}] (* Giovanni Resta, Jun 13 2016 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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a(33)-a(54) corrected by and a(55)-a(60) from Giovanni Resta, Jun 13 2016
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STATUS
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approved
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