Ramanujan's formulas of pi in Go

pi.go

package main

import (
	"fmt"
	"math"
)

func fact(n float64) float64 {
	r := float64(1)
	for 1 < n {
		r *= n
		n -= 1
	}
	return r
}

func pi1(max float64) float64 {
	modifier := 2 * math.Sqrt(2) / math.Pow(99, 2)
	sigma := float64(0)
	for n := float64(0); n <= max; n += 1 {
		numerator := fact(4 * n) * (1103 + 26490 * n)
		denominator := math.Pow(math.Pow(4, n) * math.Pow(99, n) * fact(n), 4)
		sigma += numerator / denominator
	}
	return 1 / (modifier * sigma)
}

func pi2(max float64) float64 {
	sigma := float64(0)
	for n := float64(0); n <= max; n += 1 {
		numerator := math.Pow(-1, n) * fact(4 * n) * (1123 + 21460 * n)
		denominator := math.Pow(882, 2 * n + 1) * math.Pow(math.Pow(4, n) * fact(n), 4)
		sigma += numerator / denominator
	}
	return 4 / sigma
}

func main() {
	fmt.Println(pi1(41))
	fmt.Println(pi2(41))
}