A271618 Numbers k such that 10^k-801 is prime.

3, 4, 6, 14, 15, 16, 20, 46, 52, 114, 165, 468, 504, 568, 713, 748, 899, 958, 992, 1043, 1348, 2388, 3182, 4102, 8847, 10899, 11908, 18852, 25214, 40151, 40290, 51207, 71910, 166324

Offset

1,1

Comments

For n>2, numbers such that n-3 occurrences of the digit 9 followed by the digits 199 is prime (see Example section).

a(35) > 2*10^5.

Links

Table of n, a(n) for n=1..34.

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

Makoto Kamada, Search for 9w199.

Example

6 is in this sequence because 10^6-801 = 999199 is prime.
Initial terms and primes associated:
a(1) = 3, 199;
a(2) = 4, 9199;
a(3) = 6, 999199;
a(4) = 14, 99999999999199;
a(5) = 15, 999999999999199, etc.

Mathematica

Select[Range[0, 100000], PrimeQ[10^#-801] &]

Prog

(PARI) is(n)=ispseudoprime(10^n-801) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

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

Sequence in context: A327584 A355704 A180859 * A137820 A049892 A346504

Adjacent sequences: A271615 A271616 A271617 * A271619 A271620 A271621

Keyword

nonn,more

Author

Robert Price, Apr 11 2016

Extensions

a(34) from Robert Price, Feb 14 2018

Status

approved