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 A272717 Numbers n such that (65*10^n+691)/9 is prime. 0
 1, 5, 7, 17, 35, 46, 56, 148, 187, 190, 256, 551, 553, 1033, 1751, 1976, 2696, 3116, 3364, 5353, 5893, 8063, 9548, 10640, 24655, 77992 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For n>1, numbers such that the digit 7 followed by n-2 occurrences of the digit 2 followed by the digits 99 is prime (see Example section). a(27) > 10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 72w99. EXAMPLE 5 is in this sequence because (65*10^5+691)/9 = 722299 is prime. Initial terms and primes associated: a(1) = 1, 149; a(2) = 5, 722299; a(3) = 7, 72222299; a(4) = 17, 722222222222222299; a(5) = 35, 722222222222222222222222222222222299, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(65*10^#+691)/9] &] PROG (PARI) is(n)=ispseudoprime((65*10^n+691)/9) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A290471 A261792 A166977 * A018538 A038968 A243400 Adjacent sequences:  A272714 A272715 A272716 * A272718 A272719 A272720 KEYWORD nonn,more AUTHOR Robert Price, Aug 11 2016 STATUS approved

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Last modified July 24 23:25 EDT 2021. Contains 346273 sequences. (Running on oeis4.)