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!)
 A274037 Numbers k such that 3*10^k - 49 is prime. 0
 2, 5, 6, 10, 16, 29, 35, 82, 107, 170, 185, 204, 223, 226, 388, 512, 1586, 2137, 3182, 7325, 7346, 8143, 8746, 11322, 11497, 13279, 44681, 108624, 183872 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For k>1, numbers n such that the digit 2 followed by k-2 occurrences of the digit 9 followed by the digits 51 is prime (see Example section). a(31) > 2*10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 29w51. EXAMPLE 5 is in this sequence because 3*10^5-49 = 299951 is prime. Initial terms and primes associated: a(1) = 2, 251; a(2) = 5, 299951; a(3) = 6, 2999951; a(4) = 10, 29999999951; a(5) = 16, 29999999999999951, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[3*10^# - 49] &] PROG (PARI) is(n)=ispseudoprime(3*10^n - 49) \\ Charles R Greathouse IV, Jun 08 2016 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A005984 A172186 A178761 * A227975 A123645 A057252 Adjacent sequences:  A274034 A274035 A274036 * A274038 A274039 A274040 KEYWORD nonn,more AUTHOR Robert Price, Jun 07 2016 EXTENSIONS a(28)-a(29) from Robert Price, Jul 29 2018 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 November 27 06:49 EST 2021. Contains 349365 sequences. (Running on oeis4.)