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 A271377 Numbers k such that (28*10^k - 43)/3 is prime. 0
 1, 2, 3, 4, 5, 6, 7, 13, 43, 112, 114, 127, 242, 247, 251, 335, 450, 616, 816, 1237, 1448, 4303, 4865, 5414, 6427, 9045, 10391, 12651, 25071, 27901, 50362, 58843, 67378, 68107 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For k>1, numbers such that the digit 9 followed by k-2 occurrences of the digit 3 followed by the digits 19 is prime (see Example section). a(35) > 2*10^5. LINKS Makoto Kamada, Search for 93w19. EXAMPLE 3 is in this sequence because (28*10^3 - 43)/3 = 9319 is prime. Initial terms and primes associated: a(1) = 1, 79; a(2) = 2, 919; a(3) = 3, 9319; a(4) = 4, 93319; a(5) = 5, 933319, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(28*10^# - 43)/3] &] PROG (PARI) lista(nn) = for(n=1, nn, if(ispseudoprime((28*10^n - 43)/3), print1(n, ", "))); \\ Altug Alkan, Apr 05 2016 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A032990 A060810 A319723 * A066336 A076133 A277908 Adjacent sequences:  A271374 A271375 A271376 * A271378 A271379 A271380 KEYWORD nonn,more AUTHOR Robert Price, Apr 05 2016 STATUS approved

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Last modified May 20 13:32 EDT 2022. Contains 353873 sequences. (Running on oeis4.)