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A085857

Number of 3's in decimal expansion of Fibonacci(n).

0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 0, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 1, 0, 1, 1, 1, 1, 0, 0, 2, 0, 1, 1, 2, 0, 0, 3, 2, 2, 3, 1, 0, 0, 0, 1, 1, 3, 0, 2, 2, 2, 0, 0, 0, 1, 2, 1, 1, 0, 1, 1, 1, 1, 2, 1, 0, 4, 1, 0, 1, 1, 3, 2, 2, 4, 1, 1, 2, 0, 1, 2, 2, 0, 1, 3, 2, 1, 1, 3, 2, 2, 3, 1, 1, 2, 2, 2, 3

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OFFSET

0,14

LINKS

David A. Corneth, Table of n, a(n) for n = 0..10000

EXAMPLE

From David A. Corneth, Sep 09 2025: (Start)

a(1) = 0 as Fibonacci(1) = 0 which has 0 digits 3.

a(4) = 1 as Fibonacci(4) = 3 which has 1 digit 3.

a(13) = 2 as Fibonacci(13) = 233 which has 2 digits 3. (End)

MATHEMATICA

Table[DigitCount[Fibonacci[n]][[3]], {n, 0, 200}] (* Vladimir Joseph Stephan Orlovsky, Jul 01 2011 *)