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%I #7 Oct 06 2019 18:19:56
%S 36,74,104,132,188,222,224,305,317,344,367,368,389,457,458,475,540,
%T 572,584,608,631,676,682,689,697,738,756,760,781,797,829,841,893,910,
%U 911,914,928,982,1018,1104,1122,1178,1186,1317,1328,1391,1402,1406,1518
%N Concatenations C1 and C2 are both prime (see the comment lines).
%C C1 = 'prevprime(n) followed by n followed by nextprime(n)'
%C C2 = 'nextprime(n) followed by n followed by prevprime(n)'
%H Harvey P. Dale, <a href="/A034813/b034813.txt">Table of n, a(n) for n = 0..1000</a>
%e n=797 -> previous prime is 787, next prime is 809, thus '787797809' and '809797787' are both primes.
%t c1c2Q[n_]:=Module[{ia=IntegerDigits[NextPrime[n,-1]],ib=IntegerDigits[n], ic= IntegerDigits[NextPrime[n]]}, AllTrue[{FromDigits[Join[ia,ib,ic]], FromDigits[Join[ic,ib,ia]]},PrimeQ]]; Select[Range[1600],c1c2Q] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, Apr 06 2018 *)
%Y Cf. A034808-A034821.
%K nonn,base
%O 0,1
%A _Patrick De Geest_, Oct 15 1998
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