

A294944


Numbers k such that (76*10^k + 113)/9 is prime.


0



1, 2, 4, 5, 8, 13, 14, 26, 44, 58, 61, 83, 256, 878, 1513, 3122, 6398, 6476, 8683, 18482, 33917, 45937, 64534
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

For k > 1, numbers such that the digit 8 followed by k2 occurrences of the digit 4 followed by the digits 57 is prime (see Example section).
a(24) > 2*10^5.


LINKS

Table of n, a(n) for n=1..23.
Makoto Kamada, Factorization of nearrepdigitrelated numbers.
Makoto Kamada, Search for 84w57.


EXAMPLE

2 is in this sequence because (76*10^2 + 113)/9 = 857 is prime.
Initial terms and primes associated:
a(1) = 1, 97;
a(2) = 2, 857;
a(3) = 4, 84457;
a(4) = 5, 844457;
a(5) = 8, 844444457; etc.


MATHEMATICA

Select[Range[0, 100000], PrimeQ[(76*10^# + 113)/9] &] (* Corrected by Georg Fischer, Jul 22 2019 *)


PROG

(PARI) isok(k) = isprime((76*10^k + 113)/9); \\ Michel Marcus, Nov 12 2017


CROSSREFS

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
Sequence in context: A031988 A023745 A217136 * A178656 A085443 A164571
Adjacent sequences: A294941 A294942 A294943 * A294945 A294946 A294947


KEYWORD

nonn,more,hard


AUTHOR

Robert Price, Nov 11 2017


STATUS

approved



