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A163113
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Fibonacci numbers containing equal numbers of prime digits and nonprime digits.
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0
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13, 21, 34, 1597, 2584, 6765, 121393, 514229, 14930352, 24157817, 7778742049, 365435296162, 44945570212853, 184551825793033096366333, 781774079430987230203437, 7896325826131730509282738943634332893686268675876375
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OFFSET
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1,1
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COMMENTS
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It is obvious that these numbers must contain an even number of digits.
This sequence is probably finite. The equivalent sequences in bases 4, 6, and 8 are probably infinite. - Franklin T. Adams-Watters, Aug 06 2009
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LINKS
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EXAMPLE
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24157817 is a Fibonacci number containing equal numbers of prime digits (2,5,7,7) and nonprime digits (4,1,8,1).
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MATHEMATICA
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pnpQ[n_]:=Module[{idn=IntegerDigits[n], len}, len=Length[idn]; EvenQ[len] && Count[idn, _?PrimeQ]==len/2]; Select[Fibonacci[Range[250]], pnpQ] (* Harvey P. Dale, May 01 2012 *)
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PROG
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(PARI) (mydigits(n, b=10)=local(r); r=[]; while(n>0, r=concat([n%b], r); n\=b); r); for(n=1, 500, v=mydigits(fibonacci(n)); np=sum(i=1, #v, isprime(v[i])); if(#v==2*np, print1(fibonacci(n)", ")))
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CROSSREFS
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KEYWORD
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nonn,base,changed
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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