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Task/Left-factorials/Go/left-factorials.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+    "fmt"
+    "math/big"
+)
+
+func main() {
+    fmt.Print("!0 through !10: 0")
+    one := big.NewInt(1)
+    n := big.NewInt(1)
+    f := big.NewInt(1)
+    l := big.NewInt(1)
+    next := func() { f.Mul(f, n); l.Add(l, f); n.Add(n, one) }
+    for ; ; next() {
+        fmt.Print(" ", l)
+        if n.Int64() == 10 {
+            break
+        }
+    }
+    fmt.Println()
+    for {
+        for i := 0; i < 10; i++ {
+            next()
+        }
+        fmt.Printf("!%d: %d\n", n, l)
+        if n.Int64() == 110 {
+            break
+        }
+    }
+    fmt.Println("Lengths of !1000 through !10000 by thousands:")
+    for i := 110; i < 1000; i++ {
+        next()
+    }
+    for {
+        fmt.Print(" ", len(l.String()))
+        if n.Int64() == 10000 {
+            break
+        }
+        for i := 0; i < 1000; i++ {
+            next()
+        }
+    }
+    fmt.Println()
+}