A238364 Numbers n such that 9*n^2+3*n-1 and 9*n^2+3*n+1 are twin primes.

1, 2, 5, 7, 8, 18, 22, 46, 47, 51, 77, 82, 96, 103, 117, 126, 135, 151, 152, 165, 208, 240, 266, 275, 305, 327, 366, 383, 400, 420, 436, 455, 460, 498, 516, 522, 530, 553, 582, 596, 602, 616, 712, 735, 791, 803, 817, 852, 876, 882, 883, 910, 912, 966, 975

Offset

1,2

Links

Pierre CAMI, Table of n, a(n) for n = 1..10000

Example

1*1*9+1*3-1=11; 11 and 13 are twin primes so a(1)=1.
2*2*9+2*3-1=41; 41 and 43 are twin primes so a(2)=2.

Mathematica

Select[Range[1000], AllTrue[9#^2+3#+{1, -1}, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Feb 10 2019 *)

Prog

(PARI) s=[]; for(n=1, 1000, if(isprime(9*n^2+3*n-1) && isprime(9*n^2+3*n+1), s=concat(s, n))); s \\ Colin Barker, Feb 26 2014

Crossrefs

Cf. A001097.

Sequence in context: A363626 A340326 A188341 * A342730 A227445 A216968

Adjacent sequences: A238361 A238362 A238363 * A238365 A238366 A238367

Keyword

nonn,easy

Author

Pierre CAMI, Feb 25 2014

Status

approved