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 A274238 Numbers n such that (26*10^n - 119)/3 is prime. 0
 1, 2, 3, 4, 6, 22, 25, 29, 59, 89, 221, 453, 535, 1708, 2242, 2413, 3581, 4234, 4848, 5380, 6548, 8654, 11035, 17308, 27634, 28807, 35481, 79678, 80875 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For n>1, numbers n such that the digit 8 followed by n-2 occurrences of the digit 6 followed by the digits 27 is prime (see Example section). a(30) > 10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 86w27. EXAMPLE 3 is in this sequence because (26*10^3 - 119)/3 = 8627 is prime. Initial terms and primes associated: a(1) = 1, 47; a(2) = 2, 827; a(3) = 3, 8627; a(4) = 4, 86627; a(5) = 6, 8666627, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(26*10^# - 119)/3] &] PROG (Magma) [n: n in [1..500] |IsPrime((26*10^n-119) div 3)]; // Vincenzo Librandi, Jul 07 2016 (PARI) lista(nn) = for(n=1, nn, if(ispseudoprime((26*10^n-119)/3), print1(n, ", "))); \\ Altug Alkan, Jul 08 2016 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A220702 A342503 A217351 * A115035 A219048 A329577 Adjacent sequences: A274235 A274236 A274237 * A274239 A274240 A274241 KEYWORD nonn,more AUTHOR Robert Price, Jul 06 2016 STATUS approved

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Last modified March 25 12:38 EDT 2023. Contains 361521 sequences. (Running on oeis4.)