1,2

Numbers n such that the number that begins with n, followed by

n zeros, ends with 1 is prime.

Those numbers corresponding to a(4), a(5) and a(6) are probable primes.

There is no further term up to 14000.

Do[If[PrimeQ[n*10^(n+1)+1], Print[n]], {n, 14000}]

Cf. A068817, A084428.

Sequence in context: A138417 A035357 A135059 this_sequence A164135 A119056 A164083

Adjacent sequences: A165697 A165698 A165699 this_sequence A165701 A165702 A165703

base,hard,more,nonn

F. Firoozbakht (mymontain(AT)yahoo.com), Sep 25 2009