A034591 Numbers whose concatenation with the next prime yields a prime.

0, 2, 6, 8, 9, 12, 27, 31, 36, 42, 44, 45, 51, 56, 63, 68, 69, 78, 83, 86, 93, 94, 96, 98, 102, 104, 105, 108, 115, 117, 118, 123, 126, 132, 138, 150, 151, 154, 156, 157, 160, 167, 176, 180, 183, 186, 192, 194, 195, 199, 201, 205, 213, 217, 219, 225, 230, 233

Offset

1,2

Links

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

Example

8 is a term because nextprime(8) = 11 and 811 is prime.

Maple

tcat:= (a, b) -> a*10^(1+ilog10(b))+b:
filter:= n -> isprime(tcat(n, nextprime(n))):
select(filter, [$0..200]); # Robert Israel, Jun 09 2026

Mathematica

Select[Range[0, 250], PrimeQ@FromDigits@Flatten[IntegerDigits/@{#, NextPrime@#}]&] (* Giorgos Kalogeropoulos, Jul 30 2021 *)

Prog

(PARI) isok(m) = isprime(eval(Str(m, nextprime(m+1)))); \\ Michel Marcus, Oct 03 2014 and Jul 30 2021

Crossrefs

Cf. A049852.

See also A034592, A034593, A034594, A034596, A030459.

Sequence in context: A050675 A262981 A336745 * A047278 A242204 A172209

Adjacent sequences: A034588 A034589 A034590 * A034592 A034593 A034594

Keyword

nonn,base

Author

Patrick De Geest, Oct 15 1998

Status

approved