国内外竞赛官网

https://wenku.baidu.com/view/0f46745dbed5b9f3f90f1cbc.html?rec_flag=default&fr=pc_newview_relate-1001_1-3-wk_rec_doc2-1001_1-6-0f46745dbed5b9f3f90f1cbc&sxts=1606725067527

https://artofproblemsolving.com/wiki/index.php/Category:Number_theory