# prime sequences from quadratic forms or module their discriminant

Richard Mathar mathar at strw.leidenuniv.nl
Sun Jun 8 16:45:14 CEST 2008

```A051783  and A057735 should cross-reference each other

A051783  Numbers n such that 3^n + 2 is prime.

A057735  Primes of the form 3^n + 2.

Given njas' summer vacation, I'm not submitting this directly via OEIS

Is this the right way to call attention to such pairs (and n-tuples)
in the OEIS/seqfans community?

Less interesting are the semiprime analogues:
Numbers n such that 3^n + 2 is semiprime {6, 7, 11, 12, 20, 27, 28,
40, 44, 60, ...}
Semiprimes of the form 3^n + 2 {731 = 17 * 43, 2189 = 11 * 199, 177149
= 7 * 25307, 531443 = 11 * 48313, brilliant number 3486784403 = 58027
* 60089, 7625597484989 = 11 * 693236134999, 22876792454963 = 131 *
174632003473, 12157665459056928803 = 1170408739 * 10387538177,
984770902183611232883 = 21577 * 45639843452917979,
42391158275216203514294433203 = 89 * 476305149159732623756117227, ...|

-- Jonathan Vos Post

```