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A291606
Numbers k such that 44*10^k + 3 is prime.
0
0, 1, 6, 7, 27, 51, 67, 69, 115, 153, 346, 351, 1152, 1807, 2508, 4470, 4875, 5277, 7527, 10339, 11407, 21807, 26199, 46473, 68368, 181029
OFFSET
1,3
COMMENTS
For k > 0, numbers k such that the digits 44 followed by k-1 occurrences of the digit 0 followed by the digit 3 is prime (see Example section).
a(29) > 2*10^5.
EXAMPLE
1 is in this sequence because 44*10^1 + 3 = 443 is prime.
Initial terms and associated primes:
a(1) = 0, 47;
a(2) = 1, 443;
a(3) = 6, 44000003;
a(4) = 7, 440000003;
a(5) = 27, 44000000000000000000000000003; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[44*10^# + 3] &]
PROG
(PARI) isok(k) = ispseudoprime(44*10^k + 3) \\ Altug Alkan, Aug 27 2017
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Aug 27 2017
EXTENSIONS
a(28) from Robert Price, Apr 09 2020
STATUS
approved