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URL: https://oeis.org/A228991

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A228991
Primes p such that the p-th squarefree number is prime.
0
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
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
KEYWORD
nonn
AUTHOR
Irina Gerasimova, Sep 10 2013
EXTENSIONS
Corrected by Harvey P. Dale, Jul 28 2021
STATUS
approved