A283448 Numbers k such that (265*10^k + 11)/3 is prime.

1, 2, 3, 5, 14, 18, 38, 65, 217, 218, 342, 560, 648, 962, 1151, 2043, 2113, 2641, 5738, 13295, 15793, 20424, 35729, 48474, 62298, 88077

Offset

1,2

Comments

For k > 1, numbers k such that the digits 88 followed by k-1 occurrences of the digit 3 followed by the digit 7 is prime (see Example section).

a(27) > 2*10^5.

Links

Table of n, a(n) for n=1..26.

Makoto Kamada, Factorization of near-repdigit-related numbers.

Makoto Kamada, Search for 883w7.

Example

3 is in this sequence because (265*10^3 + 11)/3 = 88337 is prime.
Initial terms and associated primes:
a(1) = 1, 887;
a(2) = 2, 8837;
a(3) = 3, 88337;
a(4) = 5, 8833337;
a(5) = 14, 8833333333333337; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(265*10^# + 11)/3] &]

Prog

(PARI) isok(n) = isprime((265*10^n + 11)/3); \\ Indranil Ghosh, Mar 09 2017

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Sequence in context: A233082 A039575 A291923 * A177901 A143743 A336273

Adjacent sequences: A283445 A283446 A283447 * A283449 A283450 A283451

Keyword

nonn,more,hard

Author

Robert Price, Mar 07 2017

Status

approved