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%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
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