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A273012
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Totient of the n-th semiprime.
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1
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2, 2, 6, 4, 6, 8, 12, 10, 20, 12, 20, 16, 24, 18, 24, 22, 42, 32, 40, 36, 28, 30, 48, 44, 36, 60, 40, 64, 42, 56, 72, 60, 46, 72, 52, 72, 88, 58, 96, 110, 60, 80, 84, 108, 66, 92, 70, 120, 112, 72, 120, 78, 104, 132, 82, 156, 116, 88, 120, 144, 160, 96, 132, 100
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OFFSET
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1,1
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COMMENTS
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If A001358(n) = p^2, then a(n) = p*(p-1).
If A001358(n) = p*q where p and q are distinct, then a(n) = (p-1)*(q-1).
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LINKS
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FORMULA
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a(n) = phi(semiprime(n)) = A000010(A001358(n)), where phi is Euler's totient function.
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EXAMPLE
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a(3) = 6 because A000010(9) = 2*3 = 6.
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MAPLE
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end proc:
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MATHEMATICA
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PROG
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(PARI) lista(nn) = for(n=1, nn, if(bigomega(n) == 2, print1(eulerphi(n), ", ")));
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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