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A352124
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Fibonacci numbers k such that pi(k) is also a Fibonacci number.
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0
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OFFSET
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1,3
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COMMENTS
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No examples larger than pi(144) = 34 are known.
Next term is > Fibonacci(123), if it exists (checked using the b-file in A054782). - Amiram Eldar, Mar 05 2022
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LINKS
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EXAMPLE
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21 is a term because 21 = Fibonacci(8) and pi(21) = 8 = Fibonacci(6).
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MATHEMATICA
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Select[(f = Fibonacci[Join[{0}, Range[2, 20]]]), MemberQ[f, PrimePi[#]] &] (* Amiram Eldar, Mar 05 2022 *)
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PROG
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(PARI) isfib(n) = my(k=n^2); k+=(k+1)<<2; issquare(k) || (n>0 && issquare(k-8));
lista(nn) = for (n=0, nn, if (n!=1, my(k=fibonacci(n)); if (isfib(primepi(k)), print1(k, ", ")))); \\ Michel Marcus, Mar 07 2022
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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