A103804 Primes p such that both 2p +/- 21 are primes.

13, 19, 29, 31, 41, 59, 79, 89, 101, 109, 131, 179, 211, 239, 241, 271, 311, 331, 349, 409, 421, 449, 499, 509, 521, 541, 601, 619, 701, 751, 821, 839, 881, 1009, 1091, 1181, 1201, 1319, 1321, 1399, 1429, 1459, 1489, 1531, 1571, 1619, 1801, 1949, 1951

Offset: 1

Author

Zak Seidov, Feb 16 2005

Keywords

• nonn

Crossrefs

Cf. A103802, A103803.

Programs

Mathematica

Select[Range[2000], PrimeQ[ # ] && PrimeQ[2# + 21] && PrimeQ[2# - 21] &]
Select[Prime[Range[4,500]],And@@PrimeQ[2#+{21,-21}]&] (* Harvey P. Dale, Dec 18 2012 *)

Formula

p, 2p-21 and 2p+21 all are positive primes.