A034810 Concatenation of 'prevprime(k) and k and nextprime(k)' is a prime.

7, 10, 13, 16, 19, 36, 37, 40, 43, 46, 58, 63, 74, 85, 88, 97, 98, 104, 125, 132, 143, 153, 156, 164, 168, 169, 175, 188, 196, 203, 206, 222, 224, 233, 241, 269, 292, 304, 305, 308, 311, 317, 331, 333, 338, 344, 359, 364, 367, 368, 372, 382, 389, 395, 397, 409

Offset: 1

Author

Patrick De Geest, Oct 15 1998

Keywords

• nonn
• base

Examples

			n=88 --> previous prime is 83, next prime is 89, thus '838889' is a prime.
		

Links

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

Crossrefs

Cf. A034808-A034821.

Programs

Mathematica

coQ[n_]:=PrimeQ[FromDigits[Flatten[IntegerDigits[{NextPrime[n,-1],n,NextPrime[n]}]]]]; Select[Range[3,409],coQ[#]&] (* Jayanta Basu, May 30 2013 *)

PARI

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

Extensions

Offset changed by Andrew Howroyd, Aug 13 2024