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

1,2

Links

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

Example

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

Maple

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

Prog

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

Crossrefs

Cf. A020338.

Sequence in context: A094058 A288134 A175966 * A105206 A080036 A242535

Adjacent sequences: A121879 A121880 A121881 * A121883 A121884 A121885

Keyword

base,easy,nonn

Author

Jason Earls, Aug 31 2006

Status

approved