A231235 Primes q of the form p^2 + 4 (p prime) such that r = q^2 + 4, s = r^2 + 4 and t = s^2 + 4 are all prime.

93738231893, 2365771484804813, 4185535280578373, 4658429282719973, 7706774555568173, 7711174427503853, 25756066576859093, 65522912397466973, 80107252841869013, 105371595617867573, 130831138562692133, 174460360753737533, 201928181545454813, 204300010667474573

Offset: 1

Author

Zak Seidov, Nov 06 2013

Keywords

• nonn

Comments

The next iteration is impossible: t^2 + 4 is divisible by 13.

Links

• Zak Seidov and Charles R Greathouse IV, Table of n, a(n) for n = 1..250 (first 100 terms from Zak Seidov)

Crossrefs

Subsequence of A231120 and A165218.

Cf. A116889.

Programs

Mathematica

extnd[p_]:=NestList[#^2+4&,p,4]; #^2+4&/@Select[Prime[ Range[ 452*10^6]],AllTrue[Rest[extnd[#]],PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 06 2021 *)

Extensions

Definition corrected by Harvey P. Dale, Jun 06 2021