1,4

Primes certified using PFGW from Primeform group

(10^1)*(2^5-1)+1=10*31+1=311 prime, 2^5-1=Mersenne-prime(3) so a(3)=1

Sequence in context: A026246 A143051 A120240 this_sequence A082361 A082363 A026177

Adjacent sequences: A102626 A102627 A102628 this_sequence A102630 A102631 A102632

nonn

Pierre CAMI (pierrecami(AT)tele2.fr), Feb 01 2005