A273868 Numbers k such that 10^k - 9^(k+1) is prime.

25, 51, 91, 107, 145, 651, 1473, 2145, 5577, 12457

Offset: 1

Author

Robert Price, Jun 01 2016

Keywords

• nonn
• more

Comments

a(11) > 10^5.

Examples

			25 is a term since 10^25 - 9^26 = 3538918110773326701067759, which is a prime number.
		

Crossrefs

Cf. A093713, A082103, A093717, A093793, A096185, A093794, A093795, A096186, A271883.

Programs

Mathematica

Select[Range[21, 100000], PrimeQ[10^# - 9^(# + 1)] &]

PARI

is(n)=ispseudoprime(10^n-9^(n+1)) \\ Charles R Greathouse IV, Jun 08 2016