A096186 Numbers k such that 10^k+9^(k-1) is prime.

1, 2, 4, 9, 12, 14, 19, 26, 28, 72, 79, 273, 565, 990, 1166, 2205, 4212, 5340, 5562, 9877, 10297, 14316, 35908, 48410, 61525

Offset: 1

Author

Herman H. Rosenfeld (herm3(AT)pacbell.net) and Robert G. Wilson v, Jun 21 2004

Keywords

• nonn

Comments

a(26) > 10^5. - Robert Price, Mar 28 2016

Crossrefs

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

Programs

Mathematica

Do[ If[ PrimeQ[10^n + 9^(n - 1)], Print[n]], {n, 4000}]

PARI

is(n)=isprime(10^n+9^(n-1)) \\ Charles R Greathouse IV, Feb 17 2017

Extensions

a(17)-a(25) from Robert Price, Mar 28 2016