A101397 Numbers k such that 4*10^k+3 is prime.

0, 1, 3, 7, 10, 40, 419, 449, 1737, 2245, 3131, 3813, 5345, 5659, 5681, 8410, 9097, 11293, 21061

Offset: 1

Author

Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005

Keywords

• nonn

Comments

See Kamada link for search limit and prime vs. PRP status.

a(20) > 2*10^5. - Robert Price, Jul 17 2015

Examples

			n = 1, 3, 7, 10 are members since 43, 4003, 40000003 and 40000000003 are prime numbers.
		

Links

• Makoto Kamada, Prime numbers of the form 400...003.
• Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.

Crossrefs

Cf. A049054, A081677, A056806, A101713.

Programs

Mathematica

Do[ If[ PrimeQ[4*10^n + 3], Print[n]], {n, 0, 10000}] (* Robert G. Wilson v, Jan 18 2005 *)

PARI

is(n)=ispseudoprime(4*10^n+3) \\ Charles R Greathouse IV, Jun 13 2017

Formula

a(n) = A101713(n-1) + 1.

Extensions

a(18)-a(19) from Kamada data by Robert Price, Dec 10 2010