0,1

next term a(23) = 47*2^583+1 > 10^177. Sequence then continues: 197, 103, 107, 881, 229, 1889, 977, 127, 131, 269, 139, 569, 293, 151, 617, 317, 163, 167, 1361, 349, 179, 23297, 373, 191, 389, 199, 809, ...

Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime

a(5)=23 because 2*5+1=11 and smallest prime of the form 11*2^m+1 is 23 (since 11+1=12 is not prime)

Cf. A032373, A057023, A057026.

Adjacent sequences: A057022 A057023 A057024 this_sequence A057026 A057027 A057028

Sequence in context: A024481 A024591 A073602 this_sequence A055469 A123151 A026133

nonn

Henry Bottomley (se16(AT)btinternet.com), Jul 24 2000