A278470 Numbers n such that 10^n - 201 is prime.

13, 20, 40, 43, 73, 85, 576, 1676

Offset

1,1

Comments

For n>2, numbers such that n-3 occurrences of the digit 9 followed by the digits 799 is prime.

a(9) > 10000. - Robert G. Wilson v, Nov 24 2016

Links

Table of n, a(n) for n=1..8.

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

Example

13 is in this sequence because 10^13 - 201 = 9999999999799 is prime.
Initial terms and primes associated:
a(1) = 13, 9999999999799;
a(2) = 20, 99999999999999999799;
a(3) = 40, 9999999999999999999999999999999999999799; etc.

Maple

A278470:=n->`if`(isprime(10^n-201), n, NULL): seq(A278470(n), n=1..10^3); # Wesley Ivan Hurt, Dec 08 2016

Mathematica

Select[Range[3, 2000], PrimeQ[10^# - 201] &]

Prog

(Magma) [n: n in [3..500] | IsPrime(10^n-201)];
(PARI) is(n)=ispseudoprime(10^n-201) \\ Charles R Greathouse IV, Jun 06 2017

Crossrefs

Cf. A108327 (10^n-21), this sequence (10^n-201), A278397 (10^n-20001), A278471 (10^n-2001).

Sequence in context: A164469 A164462 A132946 * A066515 A166656 A346401

Adjacent sequences: A278467 A278468 A278469 * A278471 A278472 A278473

Keyword

nonn,more

Author

Vincenzo Librandi, Nov 23 2016

Status

approved