A034811 - OEIS

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

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OFFSET

1,1

LINKS

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

EXAMPLE

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

MATHEMATICA

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

PROG

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

CROSSREFS