The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A275236 Numbers n such that (28*10^n-97)/3 is prime. 0
 1, 5, 8, 20, 27, 56, 74, 81, 107, 217, 294, 326, 525, 645, 667, 764, 863, 1885, 1961, 2913, 3056, 3192, 3327, 5480, 8455, 22797, 50147, 89141, 96265 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For n>1, numbers n such that the digit 9 followed by n-2 occurrences of the digit 3 followed by the digits 01 is prime (see Example section). a(30) > 10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 93w01. EXAMPLE 5 is in this sequence because (28*10^5-97)/3 = 877 is prime. Initial terms and primes associated: a(1) = 1, 61; a(2) = 5, 933301; a(3) = 8, 933333301; a(4) = 20, 933333333333333333301; a(5) = 27, 9333333333333333333333333301, etc. MATHEMATICA Select[Range[0, 100], PrimeQ[(28*10^#-97)/3 && # > 0] &] (* Corrected by Georg Fischer, Jul 22 2019 *) PROG (PARI) is(n)=ispseudoprime((28*10^n-97)/3) \\ Charles R Greathouse IV, Jul 21 2016 (MAGMA) [n: n in [1..500] | IsPrime((28*10^n-97) div 3)]; // Vincenzo Librandi, Jul 21 2016 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A271885 A295901 A143157 * A270022 A271195 A270630 Adjacent sequences:  A275233 A275234 A275235 * A275237 A275238 A275239 KEYWORD nonn,more AUTHOR Robert Price, Jul 20 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 8 06:27 EDT 2020. Contains 336290 sequences. (Running on oeis4.)