等差数列 2,5,8,11,14。。。。
(从 2 开始的 3 为公差的等差数列)
输出求等差数列前n项和
bash
输入:275
输出:113575
javascript
const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;
void (async function () {
// Write your code here
while ((line = await readline())) {
let tokens = line.split(" ");
// 从2开始
let num = [2];
for (let i = 1; i < line; i++) {
let a = num[num.length - 1] + Number(3);
num = [...num, a];
}
let sum = 0;
for (let item of num) {
sum += item;
}
console.log(sum);
}
})();