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A283684
Numbers k such that 3*10^k + 17 is prime.
0
1, 2, 5, 6, 13, 17, 24, 29, 38, 43, 59, 92, 350, 365, 679, 1016, 2958, 4434, 6306, 8819, 11687, 13484, 22189, 43034, 69354, 78146, 78631, 150182
OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 3 followed by k-2 occurrences of the digit 0 followed by the digits 17 is prime (see Example section).
a(29) > 2*10^5.
EXAMPLE
2 is in this sequence because 3*10^2 + 17 = 317 is prime.
Initial terms and associated primes:
a(1) = 1, 47;
a(2) = 2, 317;
a(3) = 5, 300017;
a(4) = 6, 3000017;
a(5) = 13, 30000000000017; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[3*10^# + 17] &]
PROG
(PARI) isok(n) = isprime((3*10^n + 17)); \\ Indranil Ghosh, Mar 14 2017
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Mar 14 2017
EXTENSIONS
a(28) from Robert Price, Jul 27 2018
STATUS
approved