3 files changed, 168 insertions, 0 deletions
diff --git a/challenge-147/pokgopun/README b/challenge-147/pokgopun/README
new file mode 100644
index 0000000000..33dfd303a4
--- /dev/null
+++ b/challenge-147/pokgopun/README
@@ -0,0 +1 @@
+Solution by PokGoPun
diff --git a/challenge-147/pokgopun/go/ch-1.go b/challenge-147/pokgopun/go/ch-1.go
new file mode 100644
index 0000000000..99dda019e8
--- /dev/null
+++ b/challenge-147/pokgopun/go/ch-1.go
@@ -0,0 +1,103 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"regexp"
+	"strconv"
+)
+
+func main() {
+	l := 20
+	if len(os.Args) > 1 {
+		i, err := strconv.Atoi(os.Args[1])
+		if err != nil {
+			log.Fatal(err)
+		}
+		l = i
+	}
+	ltp := []int{}
+	chk, nxt, _ := primeUtil()
+	re := regexp.MustCompile(`0`)
+	p := 9
+	for i := 0; i < 100; i++ {
+		p = nxt(p)
+		s := []byte(strconv.Itoa(p))
+		if re.MatchString(string(s)) {
+			continue
+		}
+		count := 1
+		for j := 1; j < len(s); j++ {
+			tp, err := strconv.Atoi(string(s[j:]))
+			if err != nil {
+				log.Fatal(err)
+			}
+			if !chk(tp) {
+				break
+			}
+			count++
+		}
+		if count == len(s) {
+			ltp = append(ltp, p)
+			if len(ltp) == l {
+				break
+			}
+		}
+	}
+	//fmt.Println(len(ltp), ltp)
+	fmt.Println(ltp)
+}
+
+func primeUtil() (func(i int) bool, func(i int) int, func()) {
+	m := map[int]bool{}
+	return func(i int) bool {
+			is, ok := m[i]
+			if ok {
+				//fmt.Println("### check prime from cache ###")
+				return is
+			} else {
+				if isPrime(i) {
+					m[i] = true
+					return true
+				}
+				m[i] = false
+				return false
+			}
+		}, func(i int) int {
+			for {
+				i++
+				is, ok := m[i]
+				if ok {
+					//fmt.Println("### check next number from cache ###")
+					if is {
+						return i
+					} else {
+						continue
+					}
+				} else {
+					if isPrime(i) {
+						m[i] = true
+						return i
+					}
+					m[i] = false
+				}
+			}
+		}, func() {
+			fmt.Println("=>", m)
+		}
+}
+func isPrime(n int) bool {
+	//fmt.Println("In isPrime")
+	if n <= 3 {
+		return n > 1
+	} else if n%2 == 0 || n%3 == 0 {
+		return false
+	}
+	for i := 5; i*i <= n; i += 6 {
+		if n%i == 0 || n%(i+2) == 0 {
+			return false
+		}
+	}
+	return true
+}
diff --git a/challenge-147/pokgopun/go/ch-2.go b/challenge-147/pokgopun/go/ch-2.go
new file mode 100644
index 0000000000..33eb44387f
--- /dev/null
+++ b/challenge-147/pokgopun/go/ch-2.go
@@ -0,0 +1,64 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+	i := 0
+	maxIdx := 3_000
+	for {
+		i++
+		if i > maxIdx-1 {
+			break
+		}
+		pi := calPtg(i)
+		j := i
+		for {
+			j++
+			if j > maxIdx {
+				break
+			}
+			pj := calPtg(j)
+			if pj+pi < calPtg(j+1) {
+				break
+			}
+			sumIdx := idxPtg(pj + pi)
+			if sumIdx > 0 {
+				diffIdx := idxPtg(pj - pi)
+				if diffIdx > 0 {
+					fmt.Printf("P(%v) + P(%v) => %v + %v = %v <= P(%v)\n", j, i, pj, pi, pj+pi, sumIdx)
+					fmt.Printf("P(%v) - P(%v) => %v - %v = %v <= P(%v)\n", j, i, pj, pi, pj-pi, diffIdx)
+					fmt.Print("\n")
+					break
+				}
+			}
+		}
+	}
+}
+
+func calPtg(i int) int {
+	return (3*i - 1) * i / 2
+}
+
+// idxPtg check if n is a Pentagon number and return its index if it is, it returns 0 if it is not
+func idxPtg(n int) int {
+	// find approximation of index of Pentagon number to start iterate up to find the actual index
+	// p = i(3i - 1)/2 => 2p = 3i^2 - i => 3i^2 = 2p + i => i^2 = 2*p/3 + i/3 => i ~~ sqrt(2*p/3)
+	i := int(math.Ceil(math.Sqrt(2 * float64(n) / 3)))
+	//fmt.Println("i=", i, "=>p=", n)
+	var p int
+	for {
+		p = (3*i - 1) * i / 2
+		if p >= n {
+			break
+		}
+		i++
+	}
+	//return p - n
+	if p-n == 0 {
+		return i
+	}
+	return 0
+}