A384174 Primes p such that the concatenations of p and 123456789 in both orders are prime.

409, 653, 881, 1091, 1489, 1913, 1993, 2039, 2729, 3677, 4073, 5039, 5507, 5683, 5849, 7349, 7789, 7907, 8419, 8623, 8689, 9973, 10429, 11057, 11617, 11689, 11821, 12527, 13367, 14033, 15259, 15511, 15629, 16139, 17569, 17881, 17911, 19373, 19577, 21187, 21383, 23197, 23399, 23629, 24043, 24317

Offset

1,1

Comments

Primes p such that both concatenations p123456789 and 123456789p are prime.

Links

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

Example

a(3) = 881 is a term because 881, 881123456789 and 123456789881 are all prime.

Maple

filter:= proc(n) isprime(n) and isprime(n*10^9+123456789) and
 isprime(123456789*10^(1+ilog10(n))+n) end proc:
select(filter, [seq(i, i=3..30000, 2)]);

Mathematica

Select[Prime[Range[5000]], PrimeQ[#*10^9 + 123456789] && PrimeQ[123456789*10^IntegerLength[#] + #] &] (* Paolo Xausa, May 23 2025 *)

Crossrefs

Intersection of A232726 and A232728.

Cf. A384218.

Sequence in context: A385768 A212604 A316934 * A052354 A213079 A260173

Adjacent sequences: A384171 A384172 A384173 * A384175 A384176 A384177

Keyword

nonn,base

Author

Robert Israel, May 22 2025

Status

approved