A034811 Concatenation of 'nextprime(k) and k and prevprime(k)' is a prime.

8, 23, 32, 36, 44, 54, 66, 74, 77, 84, 91, 104, 113, 115, 122, 130, 132, 162, 174, 178, 187, 188, 191, 204, 212, 222, 224, 232, 235, 259, 267, 281, 286, 295, 302, 305, 317, 325, 344, 353, 367, 368, 384, 389, 391, 401, 406, 427, 430, 433, 457, 458, 461, 464

Offset: 1

Author

Patrick De Geest, Oct 15 1998

Keywords

• nonn
• base

Examples

			n=353 -> next prime is 359, previous prime is 349, thus '359353349' is a prime.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A034808-A034821.

Programs

Mathematica

Select[Range[500],PrimeQ[FromDigits[Flatten[IntegerDigits/@ { NextPrime[#], #, NextPrime[ #,-1]}]]]&] (* Harvey P. Dale, Jan 12 2016 *)

PARI

isok(n)=n>2 && isprime(fromdigits(concat([digits(nextprime(n+1)), digits(n), digits(precprime(n-1))]))) \\ Andrew Howroyd, Aug 13 2024

Extensions

Offset changed by Andrew Howroyd, Aug 13 2024