RosettaCodeData/Task/Fibonacci-sequence/C/fibonacci-sequence-3.c

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2013-04-10 21:29:02 -07:00
#include <tgmath.h>
#define PHI ((1 + sqrt(5))/2)
long long unsigned fib(unsigned n) {
return floor( (pow(PHI, n) - pow(1 - PHI, n))/sqrt(5) );
}