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

1,1

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)

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 *)

Crossrefs

Subsequence of A231120 and A165218.

Cf. A116889.

Sequence in context: A217468 A234052 A104831 * A162031 A204348 A381549

Adjacent sequences: A231232 A231233 A231234 * A231236 A231237 A231238

Keyword

nonn

Author

Zak Seidov, Nov 06 2013

Extensions

Definition corrected by Harvey P. Dale, Jun 06 2021

Status

approved