The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A071403 Which squarefree number is prime? a(n)-th squarefree number equals n-th prime. 9
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 FORMULA A005117(a(n)) = A000040(n) = prime(n). a(n) ~ (6/Pi^2) * n log n. - Charles R Greathouse IV, Nov 27 2017 a(n) = A013928(A000040(n)). - Ridouane Oudra, Oct 15 2019 EXAMPLE a(25)=61 because A005117(61) = prime(25) = 97. PROG (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))=sum(k=1, sqrtint(p), p\k^2*moebius(k)) \\ Charles R Greathouse IV, Sep 13 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 CROSSREFS Cf. A005117, A013929, A000040, A000290, A013928. Sequence in context: A010385 A095037 A191284 * A010407 A035240 A278580 Adjacent sequences:  A071400 A071401 A071402 * A071404 A071405 A071406 KEYWORD nonn AUTHOR Labos Elemer, May 24 2002 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 20 15:50 EDT 2021. Contains 345165 sequences. (Running on oeis4.)