%I A034821
%S A034821 5,17,103,127,157,191,200,201,202,203,204,205,206,207,208,209,210,227,
%T A034821 234,235,236,237,238,258,259,260,261,262,307,347,354,355,356,357,358,
%U A034821 431,524,525,526,527,528,529,530,531,532,533,534,535,536,537,538,539
%N A034821 Concatenations C1 and C2 are both prime (see the comment lines).
%C A034821 C1 = 'prevprime(n) followed by nextprime(n)'
%C A034821 C2 = 'nextprime(n) followed by prevprime(n)'
%e A034821 n=17 -> next prime is 19, previous prime is 13, thus '1319' and '1913' 
               are both primes.
%Y A034821 Cf. A034808-A034820.
%Y A034821 Sequence in context: A145824 A076516 A145986 this_sequence A158007 A143562 
               A098028
%Y A034821 Adjacent sequences: A034818 A034819 A034820 this_sequence A034822 A034823 
               A034824
%K A034821 nonn,base
%O A034821 0,1
%A A034821 Patrick De Geest (pdg(AT)worldofnumbers.com), Oct 15 1998.