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A294127
Numbers k such that (44*10^k - 503)/9 is prime.
0
2, 5, 8, 10, 11, 35, 74, 107, 170, 196, 281, 748, 1124, 2597, 5189, 5650, 8453, 10822, 24554, 54596, 85370, 140410, 188999
OFFSET
1,1
COMMENTS
For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 8 followed by the digits 33 is prime (see Example section).
a(24) > 2*10^5.
EXAMPLE
2 is in this sequence because (44*10^2 - 503)/9 = 433 is prime.
Initial terms and associated primes:
a(1) = 2, 433;
a(2) = 5, 488833;
a(3) = 8, 488888833;
a(4) = 10, 48888888833;
a(5) = 11, 488888888833; etc.
MATHEMATICA
Select[Range[2, 100000], PrimeQ[(44*10^# - 503)/9] &]
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Oct 23 2017
EXTENSIONS
a(22)-a(23) from Robert Price, Dec 23 2018
STATUS
approved