OFFSET
1,1
COMMENTS
Let F(x) be the number of Fibonacci integers, A178772, less than or equal to x. Then exp(c*sqrt(log x) - (log x)^e) < F(x) < exp(c*sqrt(log x) + (log x)^(1/6 + e)) for any e > 0, where c is this constant. Luca, Pomerance, & Wagner conjecture that 1/6 can be replaced by 0, and note that it can be replaced by 1/8 on a strong form of the abc conjecture.
LINKS
Florian Luca, Carl Pomerance, Stephan Wagner, Fibonacci Integers, J. Number Theory 131 (2011), pp. 440-457. [conference version]
FORMULA
2*zeta(2)*sqrt(zeta(3)/zeta(6)/log(phi)) where phi = (1 + sqrt(5))/2 is the golden ratio.
EXAMPLE
5.1551243400746440551416193375652282874857604518811002483143110776973502988669...
MATHEMATICA
RealDigits[2 Zeta[2] Sqrt[Zeta[3]/Zeta[6]/Log[GoldenRatio]], 10, 81][[1]] (* Indranil Ghosh, Mar 19 2017 *)
PROG
(PARI) phi=(sqrt(5)+1)/2
2*zeta(2)*sqrt(zeta(3)/zeta(6)/log(phi))
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Charles R Greathouse IV, Aug 31 2016
STATUS
approved