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A153385
Number of primes <= Fibonacci(Fibonacci(n)) = pi(A007570(n)).
0
0, 0, 0, 0, 1, 3, 8, 51, 1329, 393790, 5670112879, 43416847208976911
OFFSET
0,6
FORMULA
a(n) = pi(Fibonacci(Fibonacci(n))) = A000720(A007570(n)).
a(n) = A054782(A000045(n)). - Amiram Eldar, Sep 03 2024
EXAMPLE
a(7) = 51 because Fibonacci(7) = 13, Fibonacci(13) = 233 and there are 51 primes <= 233.
MATHEMATICA
PrimePi@# & /@ (Fibonacci@Fibonacci@# & /@ Range@10) (* Robert G. Wilson v, Feb 17 2009 *)
PROG
(XiCalc) Pi(Fib(Fib(n)));
(Magma) [0] cat [#PrimesUpTo(Fibonacci(Fibonacci(n))): n in [1..9]]; // Vincenzo Librandi, Aug 02 2015
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Harry J. Smith, Dec 25 2008
EXTENSIONS
a(11) calculated using Kim Walisch's primecount and added by Amiram Eldar, Sep 03 2024
STATUS
approved