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 A275323 Numbers n such that (19*10^n + 161)/9 is prime. 0
 2, 3, 5, 6, 8, 18, 36, 59, 80, 162, 197, 200, 405, 432, 930, 1065, 1496, 1716, 3213, 5712, 6303, 7466, 14150, 23685, 54608, 59766 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For n>1, numbers n such that the digit 2 followed by n-2 occurrences of the digit 1 followed by the digits 29 is prime (see Example section). a(27) > 10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 21w29. EXAMPLE 5 is in this sequence because (19*10^5 + 161)/9 = 211129 is prime. Initial terms and primes associated: a(1) = 2, 229; a(2) = 3, 2129; a(3) = 5, 211129; a(4) = 6, 2111129; a(5) = 8, 211111129, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(19*10^# + 161)/9] &] PROG (PARI) is(n)=ispseudoprime((19*10^n+161)/9) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A088497 A088485 A194626 * A128994 A098211 A218013 Adjacent sequences:  A275320 A275321 A275322 * A275324 A275325 A275326 KEYWORD nonn,more AUTHOR Robert Price, Jul 23 2016 STATUS approved

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Last modified July 17 08:42 EDT 2019. Contains 325098 sequences. (Running on oeis4.)