Search: id:A065725
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%I A065725
%S A065725 2,3,5,17,29,31,43,59,71,127,157,197,211,227,239,241,337,353,367,379,
%T A065725 409,463,491,563,577,619,647,743,757,773,787,857,911,953,967,1093,1123,
%U A065725 1163,1193,1249,1303,1373,1429,1459,1471,1499,1583,1597,1613,1627,1669
%N A065725 Primes p such that the decimal expansion of its base 7 conversion is 
               also prime.
%C A065725 In general rebase notation (Marc LeBrun): p(n) = (7) [p] (10).
%H A065725 Harry J. Smith, <a href="b065725.txt">Table of n, a(n) for n=1,...,1000</
               a>
%e A065725 E.g. 787{10} = 2203{7} is prime but also 2203{10}.
%t A065725 Select[ Range[2500], PrimeQ[ # ] && PrimeQ[ FromDigits[ IntegerDigits[ 
               #, 7]]] & ]
%o A065725 (PARI) baseE(x, b)= { local(d, e=0, f=1); while (x>0, d=x-b*(x\b); x\=b; 
               e+=d*f; f*=10); return(e) } { n=0; for (m=1, 10^9, p=prime(m); b=baseE(p, 
               7); if (isprime(b), write("b065725.txt", n++, " ", p); if (n==1000, 
               return)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 
               27 2009]
%Y A065725 Cf. A065720 up to A065727, A065361.
%Y A065725 Sequence in context: A055472 A077499 A127061 this_sequence A057468 A127062 
               A029972
%Y A065725 Adjacent sequences: A065722 A065723 A065724 this_sequence A065726 A065727 
               A065728
%K A065725 nonn,base
%O A065725 1,1
%A A065725 Patrick De Geest (pdg(AT)worldofnumbers.com), Nov 15 2001.

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