A271361 Numbers k such that 63*10^k + 1 is prime.

1, 2, 12, 21, 27, 30, 33, 44, 46, 76, 78, 83, 84, 92, 582, 750, 787, 3218, 3290, 5617, 6385, 13960, 22705, 27636, 36497, 50349, 51169, 70381, 70486, 73096

Offset: 1

Author

Robert Price, Apr 05 2016

Keywords

• nonn
• more

Comments

Numbers k such that the digits 63 followed by k-1 occurrences of the digit 0 followed by the digit 1 is prime (see Example section).

a(31) > 10^5.

Examples

			2 is in this sequence because 63*10^2+1 = 6301 is prime.
Initial terms and associated primes:
a(1) = 1, 631;
a(2) = 2, 6301;
a(3) = 12, 63000000000001;
a(4) = 21, 63000000000000000000001;
a(5) = 27, 63000000000000000000000000001, etc.
		

Links

• Makoto Kamada, Search for 630w1.

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

Mathematica

Select[Range[0, 100000], PrimeQ[63*10^#+1] &]

PARI

is(n)=ispseudoprime(63*10^n+1) \\ Charles R Greathouse IV, Jun 13 2017