A270890 - OEIS

A270890

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

497

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

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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