A231120 Primes q of the form q = p^2 + 4 (p prime) such that r = q^2 + 4 and t = r^2 + 4 are also prime.

25877573, 124835933, 277455653, 2210598293, 2970577013, 34314969053, 43115615453, 90247970573, 93738231893, 116836126973, 153183783773, 720880808213, 1818659924933, 2068485397733, 2258777543933, 3449960763653, 3645300477293, 4501767897173, 4670625512573, 5238481845533, 6812794277693

Offset

1,1

Comments

Positions of a(n) in A165218: 16, 29, 33, 74, 78, 105, 130, 333, 520, 547, 572, 716, 740, 820, 832, 865, 975.

The first primes such that t^2+4 is also prime are 93738231893, 2365771484804813, 4185535280578373, 4658429282719973, 7706774555568173, 7711174427503853, 25756066576859093.

Links

Zak Seidov and Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 (first 699 terms from Seidov)

Prog

(PARI) forprime(p=2, 1e7, if(isprime(q=p^2+4) && isprime(r=q^2+4) && isprime(r^2+4), print1(q", "))) \\ Charles R Greathouse IV, Nov 05 2013

Crossrefs

Subsequence of A165218.

Sequence in context: A120702 A206317 A184563 * A340582 A234358 A113026

Adjacent sequences: A231117 A231118 A231119 * A231121 A231122 A231123

Keyword

nonn

Author

Zak Seidov, Nov 04 2013

Status

approved