A107771 Numbers n such that 2*n + 5 and 5*n + 2 are primes.

0, 1, 3, 7, 9, 13, 19, 21, 27, 31, 33, 39, 51, 61, 63, 67, 73, 79, 93, 97, 109, 111, 117, 123, 129, 151, 171, 177, 181, 187, 189, 217, 219, 237, 243, 247, 259, 297, 313, 319, 321, 327, 339, 357, 369, 373, 403, 417, 427, 441, 453, 457, 471, 483, 489, 493, 523, 529

Offset: 1

Author

Zak Seidov, Mar 31 2006

Keywords

• nonn

Comments

Union of A089038 and A111223.

Except for the first, all terms == 1 or 3 (mod 6). - Robert Israel, Apr 02 2020

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A089038, A111223.

Programs

Maple

select(n -> isprime(2*n+5) and isprime(5*n+2), [0,seq(i,i=1..1000,2)]); # Robert Israel, Apr 02 2020

Mathematica

Reap[Do[If[PrimeQ[2*n+5]&&PrimeQ[5*n+2],Sow[n]],{n,0,600}]][[2,1]]