%N Fibonacci's solution to x^3 + 2x^2 + 10x = 20.
%C Fibonacci attempted to solve x^3 + 2x^2 + 10x = 20 and managed to approximate an answer in base 60 with this sequence without a calculator or computer, but he gave a(6) as 40 instead of the correct answer of 38 (see A159990). Unfortunately, Fibonacci did not explain how he calculated this sequence, so it is not possible to explore the precision to a greater degree.
%D Alfred S. Posamentier & Ingmar Lehmann, The (Fabulous) Fibonacci Numbers. New York: Prometheus Books (2007): 21.
%e x = 1 + 22/60 + 7/60^2 + 42/60^3 + 33/60^4 + 4/60^5 + 40/60^6. Then x^3 + 2x^2 + 10x = 20.0000000006719323...
%Y Cf. A159990 shows the sequence corrected.
%A _Jason Chabora_, Jun 10 2014