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A287061 Numbers k such that (10^(k+3)*6319 + 863)/9 is prime (k > 0). 0
11, 19, 23, 31, 73, 257, 613, 5327, 62359 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The generated prime numbers are of the form '702'||...'1'...||'207' ('1' concatenated k times to which the prefix '702' and the suffix '207' are concatenated once).
a(1)..a(7) themselves are primes. a(10) > 80000, if it exists.
LINKS
EXAMPLE
11 is a term as (10^(11+3)*6319 + 863)/9 = 70211111111111207 is prime.
23 is a term because (10^(23+3)*6319 + 863)/9 = 70211111111111111111111111207 is prime.
MATHEMATICA
ParallelMap[ If[ PrimeQ[ (10^(#+3)*6319+863)/9], #, Nothing]&, Range[1000]]
PROG
(PARI) is(n) = ispseudoprime((10^(n+3)*6319+863)/9); \\ Altug Alkan, Jul 23 2017
CROSSREFS
Sequence in context: A320867 A165947 A129517 * A359401 A161601 A352480
KEYWORD
nonn,base,hard,more
AUTHOR
Mikk Heidemaa, May 19 2017
STATUS
approved

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Last modified July 24 20:07 EDT 2024. Contains 374585 sequences. (Running on oeis4.)