A270890 Numbers k such that (8*10^k + 49)/3 is prime.

0, 1, 2, 3, 4, 5, 6, 10, 24, 33, 34, 35, 45, 52, 56, 62, 65, 103, 166, 424, 886, 1418, 1825, 4895, 5715, 7011, 7810, 9097, 12773, 14746, 20085, 25359, 27967, 46629, 48507, 68722, 74944, 102541, 118960, 157368

Offset

1,3

Comments

For k > 2, numbers k such that the digit 2 followed by k-3 occurrences of the digit 6 followed by the digits 83 is prime (see Example section).

a(41) > 3*10^5.

Links

Table of n, a(n) for n=1..40.

Makoto Kamada, Search for 26w83.

Example

3 is in this sequence because (8*10^3 + 49)/3 = 2683 is prime.
Initial terms and associated primes:
a(1) = 0, 19;
a(2) = 1, 43;
a(3) = 2, 283;
a(4) = 3, 2683;
a(5) = 4, 26683;
a(6) = 5, 266683, etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(8*10^# + 49)/3] &]

Prog

(PARI) is(n)=isprime((8*10^n + 49)/3) \\ Charles R Greathouse IV, Feb 16 2017

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831.

Sequence in context: A271341 A306109 A281513 * A010350 A306581 A269858

Adjacent sequences: A270887 A270888 A270889 * A270891 A270892 A270893

Keyword

nonn,more

Author

Robert Price, Mar 25 2016

Extensions

a(38)-a(40) from Robert Price, May 23 2020

Status

approved