A034596 a(n) preceded and followed by nextprime(a(n)) is a prime.

5, 11, 12, 13, 15, 16, 19, 29, 30, 42, 43, 45, 46, 75, 88, 89, 97, 103, 113, 117, 125, 126, 137, 149, 150, 162, 163, 174, 198, 200, 225, 237, 252, 258, 267, 268, 273, 276, 280, 286, 323, 329, 330, 339, 346, 351, 359, 366, 374, 382, 387, 392, 393, 400, 407, 412

Offset: 1

Author

Patrick De Geest, Oct 15 1998

Keywords

• nonn
• base

Examples

			a(n)=323 -> nextprime(a(n)) is 331 so '331323331' is prime.
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..10000

Crossrefs

See also A034591-A034595.

Programs

PARI

isok(n)=my(x=digits(nextprime(n+1))); isprime(fromdigits(concat([x, digits(n), x]))) \\ Andrew Howroyd, Aug 13 2024

Extensions

Offset changed by Andrew Howroyd, Aug 13 2024