A373351 Numbers k such that there are no primes among the k-digit numbers consisting of one 1 and all other digits 9.

1, 9, 18, 21, 34, 35, 36, 39, 49, 62, 63, 69, 70, 73, 78, 80, 86, 93, 99, 102, 116, 122, 123, 141, 142, 143, 146, 147, 150, 178, 182, 185, 201, 206, 223, 230, 236, 238, 241, 246, 251, 267, 279, 285, 292, 293, 304, 309, 313, 321, 326, 329, 343, 346, 347, 350, 355, 362, 375, 380, 381, 385, 389, 398

Offset: 1

Author

Robert Israel, Jun 01 2024

Keywords

• nonn
• base

Comments

Besides 1, numbers k such that A241018(k) = 0.

Examples

			a(2) = 9 is a term because none of the numbers 199999999, 9199999999, ..., 999999991 are prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..577

Crossrefs

Cf. A241018.

Programs

Maple

filter:= proc(n) local a,j;
a:= 10^n-1;
not ormap(j -> isprime(a-8*10^j), [$0..n-1])
end proc:
select(filter, [$1..400]);