Search: id:A125524
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%I A125524
%S A125524 13,17,43,47,67,83,97,103,107,113,127,137,157,163,167,173,193,197,433,
%T A125524 443,457,463,467,487,607,613,617,643,647,653,673,677,683,823,827,853,
%U A125524 857,863,877,883,887,907,937,947,953,967,977,983,997,1013,1019,1031
%N A125524 Republican primes. Primes such that the right half of the prime is prime 
               and the left half is not.
%C A125524 If the length of n is odd then the central number is not used in the 
               calculation. So neither the left half nor the right half will contain 
               the central digit. If the length of n is even, then all numbers are 
               used.
%F A125524 Half n is the floor of the length of n divided by 2.
%e A125524 The right half of 13 is 3 which is prime. The left half is 1 which is 
               not prime.
%e A125524 The right half of 113 is 3 which is prime. The left half is 1 which is 
               not prime.
%o A125524 (PARI) \Political primes, republican case. rep(n) = { local(x,ln,y,lp,
               rp); forprime(x=2,n, y=Str(x); if(x > 9, ln=floor(length(y)/2), ln=1); 
               lp = eval(left(y,ln)); rp = eval(right(y,ln)); if(!isprime(lp)&& 
               isprime(rp),print1(x",") ) ) }
%Y A125524 Sequence in context: A043113 A043893 A068497 this_sequence A156553 A140533 
               A076789
%Y A125524 Adjacent sequences: A125521 A125522 A125523 this_sequence A125525 A125526 
               A125527
%K A125524 base,easy,nonn
%O A125524 2,1
%A A125524 Cino Hilliard (hillcino368(AT)hotmail.com), Jan 22 2007

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