A272621 Numbers n such that 10^n-9^(n-1) is prime.

3, 9, 15, 155, 217, 281, 287, 491, 563, 581, 983, 2243, 4375, 8409, 98669

Offset: 1

Author

Robert Price, May 03 2016

Keywords

• nonn
• more

Comments

a(16) > 10^5.

Examples

			3 is a member since 10^3-9^2 = 1000-81 = 919 which is a prime number.
		

Crossrefs

Cf. A093713, A082103, A093717, A093793, A096185, A093765, A093794, A093795, A096186.

Programs

Mathematica

Select[Range[0, 100000], PrimeQ[10^# - 9^(# - 1)] &]

PARI

is(n)=ispseudoprime(10^n-9^(n-1)) \\ Charles R Greathouse IV, Jun 13 2017