login
Concatenations C1 and C2 and C3 are all prime (see the comment lines).
0

%I #8 Oct 06 2019 18:17:54

%S 657,4929,10647,18291,20907,22653,27381,28053,28671,42471,48441,57363,

%T 69651,79569,89853,93261,95967,101283,110763,119481,128613,145719,

%U 149409,174993,201417,204861,205329,221883,248391,269199,272799,293451

%N Concatenations C1 and C2 and C3 are all prime (see the comment lines).

%C C1 = 'nextprime(n) followed by n'

%C C2 = 'n followed by prevprime(n)'

%C C3 = 'nextprime(n) followed by n followed by prevprime(n)'

%e n=95967 -> next prime is 95971, previous prime is 95959, thus '9597195967' and '9596795959' and '959719596795959' are all three primes.

%t ccatQ[n_]:=Module[{idn=IntegerDigits[n],pp=IntegerDigits[NextPrime[n,-1]], np= IntegerDigits[ NextPrime[n]]}, And@@PrimeQ[{FromDigits[ Join[np, idn]], FromDigits[Join[idn,pp]],FromDigits[Join[np,idn,pp]]}]]; Select[ Range[300000],ccatQ] (* _Harvey P. Dale_, Sep 09 2011 *)

%Y Cf. A034808-A034821.

%K nonn,base

%O 0,1

%A _Patrick De Geest_, Oct 15 1998