A075707 Safe primes (A005385) (p and (p-1)/2 are primes) such that 12*p+1 is also prime.

5, 23, 59, 83, 383, 479, 503, 719, 839, 863, 1619, 2039, 2099, 2579, 2819, 2879, 3023, 4139, 4259, 4679, 4703, 4919, 5879, 6719, 6779, 7559, 8039, 8783, 8819, 10799, 11279, 11423, 12203, 12659, 12899, 12983, 13523, 13799, 14159, 14303, 14699, 15683, 18119, 18443, 19259, 19379, 20183, 20663, 21059, 23663, 24083, 24239, 24659, 27239, 28163, 29123, 29339, 29483, 29759, 30803, 31139, 31583, 36923, 37463, 38603, 39119, 39503, 39839, 39983, 41879, 42299, 42443, 43403, 44519, 44939, 46679, 47339, 47819, 47963

Offset

1,1

Links

Table of n, a(n) for n=1..79.

Example

23 is a prime, so is (23-1)/2=11 and also 12*23+1=277, 59 is a prime, (59-1)/2=29 and 12*59+1=709, ...

Maple

ts_sgB_var_pras := proc(nmax) local i, tren, atek; tren := 0: for i from 1 to nmax do atek := numtheory[safeprime](i): if (atek > tren) then if (isprime(atek)='true' and isprime(6*atek+1)='true') then tren := atek: fi; fi; od; end: seq(ts_sgB_var_pras(i), i=1..3000);

Mathematica

okQ[n_]:=PrimeQ[(n-1)/2]&&PrimeQ[12n+1]
Select[Prime[Range[5000]], okQ] (* Harvey P. Dale, Nov 21 2010 *)

Crossrefs

Cf. A005384, A005385, A059455.

Sequence in context: A319087 A098499 A075565 * A126420 A246607 A116581

Adjacent sequences: A075704 A075705 A075706 * A075708 A075709 A075710

Keyword

nonn

Author

Jani Melik, Oct 02 2002

Extensions

More terms from Harvey P. Dale, Nov 21 2010

Status

approved