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 A286959 Positive numbers k such that (10^(k+3)*3277 + 3167)/9 is prime. 0
 11, 17, 197, 317, 347, 431, 977, 1949, 1991, 2913, 6317, 9725, 36599 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Or '364'||...'1'...||'463' in decimal form is prime ('1' concatenated k times to which the prefix '364' and the suffix '463' are concatenated once). a(1)..a(8) themselves are primes. LINKS Table of n, a(n) for n=1..13. EXAMPLE 11 is a term as 36411111111111463 is prime (as a string, it consists of '1' concatenated 11 times to which the prefix '364' and the suffix '463' are concatenated once). MATHEMATICA ParallelMap[ If[ PrimeQ[(10^(#+3)*3277+3167)/9], #, Nothing]&, Range[3000]] PROG (PARI) is(n)=ispseudoprime((10^(n+3)*3277+3167)/9) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Sequence in context: A166655 A262552 A279332 * A146446 A228055 A132092 Adjacent sequences: A286956 A286957 A286958 * A286960 A286961 A286962 KEYWORD nonn,hard,more,base AUTHOR Mikk Heidemaa, May 17 2017 EXTENSIONS a(13) from Giovanni Resta, May 25 2017 STATUS approved

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Last modified September 7 17:00 EDT 2024. Contains 375749 sequences. (Running on oeis4.)