摘要：
1137. N-th Tribonacci Number Difficulty: 简单 The Tribonacci sequence Tn is defined as follows: T0 = 0, T1 = 1, T2 = 1, and Tn+3 = Tn + Tn+1 + Tn+2 for 阅读全文
摘要：
509. Fibonacci Number Difficulty: 简单 The Fibonacci numbers, commonly denoted F(n) form a sequence, called the Fibonacci sequence, such that each numbe 阅读全文