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 A271882 Numbers n such that (10^n + 101)/3 is prime. 0
 1, 2, 3, 6, 9, 12, 23, 39, 59, 168, 198, 203, 231, 449, 863, 920, 1064, 1484, 1674, 2018, 2943, 3123, 4073, 4122, 8360, 11774, 16031, 26507, 31146, 33170, 44952, 62402, 88020, 89687 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For n>1, numbers that begin with n-2 occurrences of the digit 3 followed by the digits 67 is prime (see Example section). a(35) > 2*10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 3w67. EXAMPLE 3 is in this sequence because (10^3+101)/3 = 367 is prime. Initial terms and primes associated: a(1) = 1, 37; a(2) = 2, 67; a(3) = 3, 367; a(4) = 6, 333367; a(5) = 9, 333333367, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(10^#+101)/3] &] PROG (PARI) lista(nn) = for(n=1, nn, if(ispseudoprime((10^n+101)/3), print1(n, ", "))); \\ Altug Alkan, Apr 16 2016 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A298435 A261539 A325552 * A123316 A303365 A096845 Adjacent sequences:  A271879 A271880 A271881 * A271883 A271884 A271885 KEYWORD nonn,more AUTHOR Robert Price, Apr 16 2016 STATUS approved

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Last modified January 22 19:16 EST 2020. Contains 331153 sequences. (Running on oeis4.)