1,1

n such that (3^n+1)/2 is prime: 1, 2, 4, 16, 32, 64.

Primes can only occur for n=2^k. - Don Reble (djr(AT)nk.ca), April 28 2004. The next term (if it exists) has k>=21 (i.e. more than 10^6 decimal digits).

a(3)=41 because it can be written as (3^4+1)/2=82/2.

Sequence in context: A054859 A076725 A059917 this_sequence A042447 A075872 A075891

Adjacent sequences: A093622 A093623 A093624 this_sequence A093626 A093627 A093628

nonn,hard

Hugo Pfoertner (hugo(AT)pfoertner.org), Apr 19 2004