A034811 - OEIS

%I #11 Aug 13 2024 22:53:56

%S 8,23,32,36,44,54,66,74,77,84,91,104,113,115,122,130,132,162,174,178,

%T 187,188,191,204,212,222,224,232,235,259,267,281,286,295,302,305,317,

%U 325,344,353,367,368,384,389,391,401,406,427,430,433,457,458,461,464

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

%H Harvey P. Dale, <a href="/A034811/b034811.txt">Table of n, a(n) for n = 1..1000</a>

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

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

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

%Y Cf. A034808-A034821.

%K nonn,base

%O 1,1

%A _Patrick De Geest_, Oct 15 1998

%E Offset changed by _Andrew Howroyd_, Aug 13 2024