1,3

Do[ If[ PrimeQ[ 2*9^n + 1], Print[ n ]], {n, 0, 1000}]

Cf. A003306 (n such that 2*3^n + 1 is prime).

Sequence in context: A128035 A003473 A095373 this_sequence A026698 A099428 A099920

Adjacent sequences: A056799 A056800 A056801 this_sequence A056803 A056804 A056805

nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 22 2000

More terms from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Apr 22 2003