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A294570
Numbers k such that (58*10^k + 329)/9 is prime.
0
0, 1, 3, 6, 19, 22, 27, 48, 70, 130, 364, 594, 603, 799, 2442, 3168, 5059, 5563, 6523, 12282, 13498, 34099, 86242, 122170, 161691
OFFSET
1,3
COMMENTS
For k > 1, numbers k such that the digit 6 followed by k-2 occurrences of the digit 4 followed by the digits 81 is prime (see Example section).
a(26) > 2*10^5.
EXAMPLE
3 is in this sequence because (58*10^3 + 329)/9 = 6481 is prime.
Initial terms and associated primes:
a(1) = 0, 43;
a(2) = 1, 101;
a(3) = 3, 6481;
a(4) = 6, 6444481;
a(5) = 19, 64444444444444444481; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(58*10^# + 329)/9] &]
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Nov 02 2017
EXTENSIONS
a(24)-a(25) from Robert Price, May 01 2019
STATUS
approved