A228991 Primes p such that the p-th squarefree number is prime.

2, 3, 13, 29, 31, 37, 61, 67, 71, 103, 109, 139, 149, 167, 191, 223, 229, 241, 257, 263, 269, 271, 347, 349, 367, 379, 457, 461, 487, 577, 607, 673, 701, 761, 797, 809, 907, 911, 967, 983, 1019, 1031, 1033, 1049, 1063, 1097, 1103, 1109, 1283, 1303, 1423

Offset

1,1

Links

Table of n, a(n) for n=1..51.

Mathematica

Module[{nn=2500, sqf}, sqf=Select[Range[nn], SquareFreeQ]; Select[Prime[ Range[ PrimePi[Length[sqf]]]], PrimeQ[sqf[[#]]]&]] (* Harvey P. Dale, Jul 28 2021 *)

Prog

(PARI) lista(nn) = my(sqfs = select(n->issquarefree(n), vector(nn, i, i))); forprime(p = 2, #sqfs, if (isprime(sqfs[p]), print1(p, ", "))) \\ Michel Marcus, Sep 11 2013

Crossrefs

Cf. A005117.

Subsequence of A071403.

Sequence in context: A029737 A191063 A105891 * A141585 A191021 A106867

Adjacent sequences: A228988 A228989 A228990 * A228992 A228993 A228994

Keyword

nonn

Author

Irina Gerasimova, Sep 10 2013

Extensions

Corrected by Harvey P. Dale, Jul 28 2021

Status

approved