A030458 Primes formed by concatenating n with n+1.

23, 67, 89, 1213, 3637, 4243, 5051, 5657, 6263, 6869, 7879, 8081, 9091, 9293, 9697, 102103, 108109, 120121, 126127, 138139, 150151, 156157, 180181, 186187, 188189, 192193, 200201, 216217, 242243, 246247, 252253, 270271, 276277, 278279, 300301, 308309, 312313, 318319

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• base

Comments

Primes in A030656.

Links

• Paul Tek, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A052089, A052087, A052088.

Programs

Magma

[m: n in [2..270 by 2] | IsPrime(m) where m is Seqint(Intseq(n+1) cat Intseq(n))];  // Bruno Berselli, Jun 18 2011

Mathematica

Select[Table[FromDigits[Join[Flatten[IntegerDigits[{n,n+1}]]]],{n,270}],PrimeQ] (* Jayanta Basu, May 16 2013 *)

PARI

forstep(n=2,1e3,2,if(isprime(k=eval(Str(n,n+1))),print1(k", "))) \\ Charles R Greathouse IV, Jun 18 2011

Python

from sympy import isprime
from itertools import count, islice
def agen(): yield from filter(isprime, (int(str(k)+str(k+1)) for k in count(2, 2)))
print(list(islice(agen(), 38))) # Michael S. Branicky, Aug 05 2022