A157359 Quatro-safe primes.

47, 1439, 2879, 858239, 861599, 982559, 1014719, 1067999, 2029439, 2034239, 2297759, 2683679, 2978399, 3301919, 4068479, 4288799, 4737599, 5454719, 6484319, 6753119, 7145759, 8624159, 9511199, 9717119, 10533599, 10739999

Offset

1,1

Comments

(47-1)/2=23,(23-1)/2=11,(11-1)/2=5,(5-1)/2=2(prime),...

Links

Table of n, a(n) for n=1..26.

Mathematica

lst={}; Do[p=Prime[n]; If[PrimeQ[a=(p-1)/2]&&PrimeQ[b=(a-1)/2]&&PrimeQ[c=(b-1)/2]&&PrimeQ[(c-1)/2], AppendTo[lst, p]], {n, 10!}]; lst
Select[Prime[Range[711000]], AllTrue[Rest[NestList[(#-1)/2&, #, 4]], PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Dec 31 2018 *)

Crossrefs

Cf. A005385, A066179, A157357, A157358

Sequence in context: A009069 A348805 A285237 * A153214 A142845 A202128

Adjacent sequences: A157356 A157357 A157358 * A157360 A157361 A157362

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Feb 27 2009

Status

approved