题解 | #等差数列#
等差数列
http://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
while(line = readline()) {
const num = parseInt(line);
let total = 0;
for (let i = 2; i <= 2 + 3*(num-1); i = i+3) {
total += i;
}
print(total);
}