斐波那契数列
function fib(n){
let num=0
if(n<=2){
return num=1
}
return num=fib(n-1)+fib(n-2)
}
斐波那契数列求和
function fibSum(n) {
let num = 0,
a = 1,
b = 1,
sum = 0;
if (n <= 2) {
return sum = n === 1 ? 1 : 2
}
for(let i=3;i<=n;i++){
num=a+b;
a=b;
b=num
sum+=num
}
return sum+2
}
阶乘
function jc(n){
let num=1
for(let i=1;i<=n;i++){
num*=i
}
return num
}
阶乘求和
function jc(n) {
let num = 1,
sum = 0
for (let m = 0; m < n; m++) {
for (let i = 1; i <= n; i++) {
num *= i
sum += num
}
return sum
}
}
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