A121882 Numbers k such that k + D(k) + 1 is prime, where D() are the doublets, A020338.

1, 3, 5, 6, 8, 9, 10, 11, 13, 14, 15, 21, 23, 25, 28, 30, 31, 34, 35, 36, 38, 45, 49, 50, 53, 60, 63, 64, 66, 69, 71, 74, 76, 79, 80, 81, 83, 90, 91, 99, 101, 105, 106, 108, 110, 113, 114, 124, 128, 130, 134, 135, 136, 140, 141, 143, 144, 150, 151, 159, 161, 163, 165

Offset: 1

Author

Jason Earls, Aug 31 2006

Keywords

• base
• easy
• nonn

Examples

			9 is a term because 9 + 99 + 1 = 109 is prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A020338.

Programs

Maple

filter:= n -> isprime(1+n*(2+10^(1+ilog10(n)))):
select(filter, [$1..1000]);# Robert Israel, Feb 23 2022

PARI

isok(k) = isprime(k + eval(Str(k, k)) + 1); \\ Michel Marcus, Feb 25 2022