|Bill Allombert on Fri, 08 Jan 2016 19:35:35 +0100|
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|Re: fibonacci(n) for large n's|
On Fri, Jan 08, 2016 at 06:25:00PM +0000, email@example.com wrote: > Whether or not you're working modulo something, consider > the 2x2 > matrix M = [0 1] [1 1] , ie with all Mij = 1 except for M11 = 0 . One simpler and faster way is myfibo(n)=polcoeff(lift(Mod(x,x^2-x-1)^n),1) which you can restrict mod m: myfibomod(n,m)=polcoeff(lift(Mod(x*Mod(1,m),x^2-x-1)^n),1) Cheers, Billl.