1,2

This corresponds to the numbers such that 3m^m+1 is prime, but these must all be even, m=2n, and therefore it is more natural to record the sequence of n=m/2.

a(1) = 1, because 2^2*3+1 = 13 is the smallest prime of this form.

a(2) = 2, because 4^4*3+1 = 769 is the next smallest prime of this form. a(3) = 3, because 6^6*3+1 = 139969 is again a prime.

(PARI) for(i=1, 9999, ispseudoprime(i^i*3+1)&print1(i/2, ", "))

Cf. A065798, A160360.

Sequence in context: A067799 A117702 A041343 this_sequence A064936 A041655 A082520

Adjacent sequences: A160597 A160598 A160599 this_sequence A160601 A160602 A160603

hard,more,nonn

M. F. Hasler (MHasler(AT)univ-ag.fr), Jul 10 2009