feat: add fibonacci sequence

README.md

@@ -8,6 +8,7 @@
 | ChudnovskyAlgorithm     | 楚德诺夫斯基算法           | [chudnovsky-algorithm](https://hatter.ink/static/resource/muboard/?id=chudnovsky-algorithm&version=latest&full=1)           |
 | EulerNumber             | 欧拉数                | [eulers-number](https://hatter.ink/static/resource/muboard/?id=eulers-number&version=latest&full=1)                         |
 | EulerTheorem            | 欧拉定理               | [euler-theorem](https://hatter.ink/static/resource/muboard/?id=euler-theorem&version=latest&full=1)                         |
+| FibonacciSequence       | 斐波那契数列             | [fibonacci-sequence](https://hatter.ink/static/resource/muboard/?id=fibonacci-sequence&version=latest&full=1)               |
 | LeibnizFormula          | $\pi$ 的莱布尼茨公式      | [leibniz-formula](https://hatter.ink/static/resource/muboard/?id=leibniz-formula&version=1)                                 |
 | ModularInv              | 求乘法逆元【扩展欧几里得法】     | -                                                                                                                           |
 | Prime                   | 试除法                | -                                                                                                                           |

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

@@ -0,0 +1,35 @@
+package me.hatter.math;
+
+import me.hatter.math.util.MathUtil;
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.math.RoundingMode;
+import java.util.ArrayList;
+import java.util.List;
+
+public class FibonacciSequence {
+    static final BigDecimal SQRT5 = MathUtil.sqrt(BigDecimal.valueOf(5), 100);
+
+    public static void main(String[] args) {
+        List<BigInteger> nums = new ArrayList<>();
+        List<BigInteger> num2s = new ArrayList<>();
+        for (int i = 0; i < 20; i++) {
+            nums.add(fn(i));
+            num2s.add(fn2(i));
+        }
+        System.out.println(nums);
+        System.out.println(num2s);
+    }
+
+    public static BigInteger fn(int n) {
+        BigDecimal a = BigDecimal.ONE.add(SQRT5).divide(BigDecimal.valueOf(2), 100, RoundingMode.HALF_UP);
+        BigDecimal b = BigDecimal.ONE.subtract(SQRT5).divide(BigDecimal.valueOf(2), 100, RoundingMode.HALF_UP);
+        return a.pow(n).subtract(b.pow(n)).divide(SQRT5, 0, RoundingMode.HALF_UP).toBigInteger();
+    }
+
+    public static BigInteger fn2(int n) {
+        BigDecimal a = BigDecimal.ONE.add(SQRT5).divide(BigDecimal.valueOf(2), 100, RoundingMode.HALF_UP);
+        return a.pow(n).divide(SQRT5, 0, RoundingMode.HALF_UP).toBigInteger();
+    }
+}