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A271361
Numbers k such that 63*10^k + 1 is prime.
0
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
1,2
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.
EXAMPLE
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.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[63*10^#+1] &]
PROG
(PARI) is(n)=ispseudoprime(63*10^n+1) \\ Charles R Greathouse IV, Jun 13 2017
KEYWORD
nonn,more
AUTHOR
Robert Price, Apr 05 2016
STATUS
approved