🚀 go-pugleaf

Daniel G Millar (dmillar@sas.upenn.edu) wrote:
: Although I did not read the original post, I thought I may be able to
: assist Mr. Dunton with an easy program to find the nth Finonacci number.
: Pat Mara showed an intuitive recursive method- so I shall address a
: NONrecursive method.  There is the program I quickly wrote on my TI-81.

: (1+5^(1/2))/2->A
: (1-5^(1/2))/2->B
: Disp "Fib Num?"
: Input N
: (1/5^(1/2))(A^N-B^N)->X
: Disp X

: The output is the Nth Fibonacci number.


: ...Dan
: dmillar@mail.sas.upenn.edu

	What you have programmed is part of a Lucas Sequence and finding
the Nth Fibonacci number can actually be found more easily if you use
matrices.

	If you define a matrix as

                        | 1  1 |
                        | 1  0 |

 and raise it to the N power the upper right and lower left numbers will
be the Nth Fibonacci numbers.