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A287351
Numbers k such that (10^k*361 - 163)/9 is prime (k > 0).
0
1, 3, 9, 15, 27, 37, 165, 207, 897, 5761, 16753, 17995, 96567
OFFSET
1,2
COMMENTS
a(14) > 10^5. - Robert Price, Oct 31 2017
EXAMPLE
If k = 1 then (10^1*361 - 163)/9 = 383 (prime), so 1 is a term.
If k = 9 then (10^9*361 - 163)/9 = 40111111093 (prime), so 9 is a term.
MATHEMATICA
ParallelMap[ If[ PrimeQ[ (10^# 361-163)/9], #, Nothing] &, Range[6000]]
CROSSREFS
Cf. A247643.
Sequence in context: A087031 A089632 A247643 * A256388 A082897 A363523
KEYWORD
nonn,hard,more
AUTHOR
Mikk Heidemaa, May 23 2017
EXTENSIONS
a(13) from Robert Price, Oct 31 2017
STATUS
approved