rt=read.table(paste0(A,".txt"),header=F,sep="\t",check.names=F) Error in paste0(A, ".txt") : object 'A' not found

# -*- coding: utf-8 -*-
"""
Created on Wed Nov 25 15:52:51 2020

@author: 
"""

Fib = [1.0, 1.0]  # 初始化前两个元素为1
for i in range(2, 20):  # 计算Fibonacci数列
    Fib.append(Fib[i-1]+Fib[i-2])

print("Fibonacci数列为：")  # 输出Fibonacci数列
for i in range(20):
    print("%d" % Fib[i], end="\t")  # 每个数输出后加制表符
    if (i+1) % 4 == 0:  # 每行输出4个数
        print()  # 输出换行符

程序运行截图：