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A352124
Fibonacci numbers k such that pi(k) is also a Fibonacci number.
0
0, 1, 2, 3, 5, 21, 144
OFFSET
1,3
COMMENTS
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
EXAMPLE
21 is a term because 21 = Fibonacci(8) and pi(21) = 8 = Fibonacci(6).
MATHEMATICA
Select[(f = Fibonacci[Join[{0}, Range[2, 20]]]), MemberQ[f, PrimePi[#]] &] (* Amiram Eldar, Mar 05 2022 *)
PROG
(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
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Marc Kouyoumdjian, Mar 05 2022
STATUS
approved