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A075707 Safe primes (A005385) (p and (p-1)/2 are primes) such that 12*p+1 is also prime. 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified February 23 08:18 EST 2019. Contains 320420 sequences. (Running on oeis4.)