The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A293000 Numbers k such that (2*10^k - 23)/3 is prime. 0
 2, 3, 4, 26, 44, 58, 73, 88, 211, 244, 1393, 2282, 4108, 6777, 7480, 14369, 16153, 21081, 24308, 27368, 43455, 51597, 55559, 67405, 88112, 148460, 288371, 297488 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For k>1, numbers k-2 occurrences of the digit 6 followed by the digits 59 is prime (see Example section). a(29) > 3*10^5. LINKS Table of n, a(n) for n=1..28. Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 6w59 EXAMPLE 4 is in this sequence because (2*10^4 - 23)/3 = 6659 is prime. Initial terms and associated primes: a(1) = 2, 59; a(2) = 3, 659; a(3) = 4, 6659; a(4) = 26, 66666666666666666666666659; a(5) = 44, 66666666666666666666666666666666666666666659; etc. MATHEMATICA Select[Range[1, 100000], PrimeQ[(2*10^# - 23)/3] &] CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A171558 A044906 A255312 * A141565 A098549 A274677 Adjacent sequences: A292997 A292998 A292999 * A293001 A293002 A293003 KEYWORD nonn,more,hard AUTHOR Robert Price, Sep 27 2017 EXTENSIONS a(26) from Robert Price, Apr 24 2018 a(27)-a(28) from Robert Price, Jun 01 2023 STATUS approved

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

Last modified April 21 03:36 EDT 2024. Contains 371850 sequences. (Running on oeis4.)