feat: add telescoping sum

src/main/java/me/hatter/math/TelescopingSum.java

@@ -0,0 +1,15 @@
+package me.hatter.math;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+public class TelescopingSum {
+    // https://hatter.ink/static/resource/muboard/?id=telescoping-sum&version=latest&full=1
+    public static void main(String[] args) {
+        BigDecimal d = BigDecimal.valueOf(0);
+        for (long i = 1; i < 100000; i++) {
+            d = d.add(BigDecimal.ONE.divide(BigDecimal.valueOf(i).multiply(BigDecimal.valueOf(i + 1)), 100, RoundingMode.HALF_UP));
+        }
+        System.out.println(d);
+    }
+}