A286959 Positive numbers k such that (10^(k+3)*3277 + 3167)/9 is prime.

11, 17, 197, 317, 347, 431, 977, 1949, 1991, 2913, 6317, 9725, 36599

Offset

1,1

Comments

Or '364'||...'1'...||'463' in decimal form is prime ('1' concatenated k times to which the prefix '364' and the suffix '463' are concatenated once).

a(1)..a(8) themselves are primes.

Links

Table of n, a(n) for n=1..13.

Example

11 is a term as 36411111111111463 is prime (as a string, it consists of '1' concatenated 11 times to which the prefix '364' and the suffix '463' are concatenated once).

Mathematica

ParallelMap[ If[ PrimeQ[(10^(#+3)*3277+3167)/9], #, Nothing]&, Range[3000]]

Prog

(PARI) is(n)=ispseudoprime((10^(n+3)*3277+3167)/9) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A166655 A262552 A279332 * A146446 A228055 A132092

Adjacent sequences: A286956 A286957 A286958 * A286960 A286961 A286962

Keyword

nonn,hard,more,base

Author

Mikk Heidemaa, May 17 2017

Extensions

a(13) from Giovanni Resta, May 25 2017

Status

approved