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A281829
Numbers k such that 4*10^k + 93 is prime.
0
0, 3, 4, 5, 6, 16, 20, 21, 27, 29, 68, 81, 89, 100, 125, 388, 737, 869, 1398, 2614, 8111, 14777, 15696, 22299, 42423, 52272, 84346, 157150, 180360
OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 0 followed by the digits 93 is prime (see Example section).
a(30) > 2*10^5.
EXAMPLE
4 is in this sequence because 4*10^4 + 93 = 40093 is prime.
Initial terms and associated primes:
a(1) = 0, 97;
a(2) = 3, 4093;
a(3) = 4, 40093;
a(4) = 5, 400093;
a(5) = 6, 4000093; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[4*10^# + 93] &]
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Jan 31 2017
EXTENSIONS
a(28)-a(29) from Robert Price, Aug 13 2018
STATUS
approved