Data commit

Task/Ultra-useful-primes/Go/ultra-useful-primes.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+    "fmt"
+    big "github.com/ncw/gmp"
+)
+
+var two = big.NewInt(2)
+
+func a(n uint) int {
+    one := big.NewInt(1)
+    p := new(big.Int).Lsh(one, 1 << n)
+    p.Sub(p, one)
+    for k := 1; ; k += 2 {
+        if p.ProbablyPrime(15) {
+            return k
+        }
+        p.Sub(p, two)
+    }
+}
+
+func main() {
+    fmt.Println(" n   k")
+    fmt.Println("----------")
+    for n := uint(1); n < 14; n++ {
+        fmt.Printf("%2d   %d\n", n, a(n))
+    }
+}