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A071403
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Which squarefree number is prime? a(n)-th squarefree number equals n-th prime.
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10
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2, 3, 4, 6, 8, 9, 12, 13, 16, 18, 20, 24, 27, 29, 31, 33, 37, 38, 42, 45, 46, 50, 52, 56, 61, 62, 64, 67, 68, 71, 78, 81, 84, 86, 92, 93, 96, 100, 103, 105, 109, 110, 117, 118, 121, 122, 130, 139, 141, 142, 145, 149, 150, 154, 158, 162, 166, 167, 170, 172, 174, 180
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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a(25)=61 because A005117(61) = prime(25) = 97.
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MATHEMATICA
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Position[Select[Range[300], SquareFreeQ], _?PrimeQ][[All, 1]] (* Michael De Vlieger, Aug 17 2023 *)
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PROG
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(PARI) lista(nn)=sqfs = select(n->issquarefree(n), vector(nn, i, i)); for (i = 1, #sqfs, if (isprime(sqfs[i]), print1(i, ", ")); ); \\ Michel Marcus, Sep 11 2013
(PARI) a(n, p=prime(n))=my(s); forfactored(k=1, sqrtint(p), s+=p\k[1]^2*moebius(k)); s \\ Charles R Greathouse IV, Nov 27 2017
(PARI) first(n)=my(v=vector(n), pr, k); forsquarefree(m=1, n*logint(n, 2)+3, k++; if(m[2][, 2]==[1]~, v[pr++]=k; if(pr==n, return(v)))) \\ Charles R Greathouse IV, Jan 08 2018
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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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