A084671 Primes such that the decimal concatenation of prime(n) and n is prime.

5, 23, 67, 73, 157, 307, 389, 419, 449, 587, 661, 751, 1051, 1229, 1297, 1303, 1327, 1823, 1913, 1999, 2131, 2179, 2207, 2239, 2371, 2689, 2699, 3067, 3433, 3593, 3623, 3719, 3919, 3943, 4001, 4073, 4229, 4241, 4397, 4591, 4733, 4919, 4957, 4987, 5393, 5449, 5503

Offset

1,1

Links

Michael S. Branicky, Table of n, a(n) for n = 1..10000

Example

23 is a term because 23=prime(9) and concatenation of 23 and 9 is prime.

Mathematica

a=ParallelTable[Prime[k], {k, 1, 10^6}]; k=2; Monitor[Parallelize[While[True, If[ToExpression[StringJoin[ToString/@{k, FromDigits[Position[a, k]//Flatten]}]]//PrimeQ, Print[k]]; k++]; k], k] (* J.W.L. (Jan) Eerland, Dec 22 2022 *)

Prog

(Python)
from itertools import islice
from sympy import isprime, sieve
def agen(): yield from (pn for n, pn in enumerate(sieve, 1) if isprime(int(str(pn)+str(n))))
print(list(islice(agen(), 52))) # Michael S. Branicky, Dec 22 2022

Crossrefs

Sequence in context: A331987 A241765 A106956 * A284648 A290187 A243442

Adjacent sequences: A084668 A084669 A084670 * A084672 A084673 A084674

Keyword

nonn,base

Author

Zak Seidov, Jun 29 2003

Extensions

Edited by Charles R Greathouse IV, Apr 27 2010

a(45)-a(52) from J.W.L. (Jan) Eerland, Dec 22 2022

Status

approved