

A110581


Primes p such that 2p1 is prime, but 4p3 is not prime.


3



3, 7, 31, 37, 97, 139, 157, 199, 211, 229, 271, 307, 337, 367, 379, 547, 577, 601, 607, 661, 691, 727, 811, 877, 937, 967, 997, 1009, 1171, 1237, 1297, 1399, 1429, 1459, 1609, 1627, 1657, 1759, 1867, 2011, 2029, 2137, 2221, 2281, 2467, 2539, 2551, 2557
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OFFSET

1,1


COMMENTS

A subsequence of A005382, primes p such that 2p1 is also prime. Note that for all n, 2a(n)1 is not in this sequence.


LINKS

T. D. Noe, Table of n, a(n) for n=1..1000
Jeffery J. Holt, The minimal number of solutions to phi(n)=phi(n+k), Math. Comp., 72 (2003), 20592061.


MATHEMATICA

Select[Prime[Range[2, 1000]], PrimeQ[2#1] && !PrimeQ[4#3]&]


PROG

(MAGMA) [p: p in PrimesUpTo(2600)  IsPrime(2*p1) and not IsPrime(4*p3)]; // Vincenzo Librandi, Apr 14 2013


CROSSREFS

Sequence in context: A080173 A023266 A217198 * A128436 A213899 A034915
Adjacent sequences: A110578 A110579 A110580 * A110582 A110583 A110584


KEYWORD

nonn,easy


AUTHOR

T. D. Noe, Jul 28 2005


STATUS

approved



