A158708 Primes p such that p + floor(p/2) is prime.

2, 5, 13, 29, 41, 53, 73, 101, 109, 149, 181, 233, 281, 293, 349, 401, 409, 421, 449, 461, 541, 569, 613, 661, 673, 701, 709, 769, 809, 821, 853, 881, 953, 1021, 1033, 1109, 1129, 1193, 1201, 1249, 1289, 1301, 1409, 1429, 1453, 1481, 1493, 1669, 1693, 1789

Offset

1,1

Comments

Apart from the first term, primes of the form 4n+1 such that 6n+1 is also prime. [Charles R Greathouse IV, Nov 09 2011]

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Mathematica

lst={}; Do[p=Prime[n]; If[PrimeQ[Floor[p/2]+p], AppendTo[lst, p]], {n, 6!}]; lst
Select[Prime[Range[300]], PrimeQ[Floor[# / 2] + #]&] (* Vincenzo Librandi, Apr 15 2013 *)

Prog

(PARI) forprime(p=2, 1e4, if(isprime(p+p\2), print1(p", "))) \\ Charles R Greathouse IV, Nov 09 2011
(PARI) print1(2); forprime(p=3, 1e4, if(p%4==1&&isprime(p\4*6+1), print1(", "p))) \\ Charles R Greathouse IV, Nov 09 2011
(Magma) [p: p in PrimesUpTo(1800) | IsPrime(p+ (p div 2))]; // Vincenzo Librandi, Apr 15 2013

Crossrefs

Sequence in context: A002559 A049097 A045366 * A093702 A011756 A050950

Adjacent sequences: A158705 A158706 A158707 * A158709 A158710 A158711

Keyword

nonn,easy

Author

Vladimir Joseph Stephan Orlovsky, Mar 24 2009

Status

approved