A330699 Primes p such that the base-10 concatenation p||(p+1)||p is prime.

7, 11, 13, 37, 41, 47, 59, 61, 71, 79, 83, 101, 103, 149, 181, 191, 193, 229, 241, 307, 317, 347, 359, 373, 383, 409, 439, 467, 487, 509, 569, 691, 823, 839, 857, 907, 941, 1061, 1069, 1091, 1109, 1123, 1181, 1193, 1303, 1423, 1447, 1487, 1499, 1579, 1601, 1697, 1777, 1831, 1871, 1931, 1949, 1979

Offset: 1

Author

Robert Israel, Dec 26 2019

Keywords

• nonn
• base

Examples

			a(3)=13 is a member because 13 and 131413 are primes.
		

Links

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

Crossrefs

Cf. A261618, A309935.

Programs

Maple

f:= proc(n) local d; d:=10^(ilog10(n)+1);
   n*(d^2+d+1)+d
end proc:
select(t -> isprime(t) and isprime(f(t)), [seq(i,i=3..10000,2)]);