0-20:
二进制:0,1,10,11,100,101,110,111,1000,1001,1010,1011,1100,1101,1110,
1111,10000,10001,10010,10011,10100
三进制:0,1,2,10,11,12,20,21,22,100,101,102,110,111,112,120,121,122,200,201,202
十六进制:0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,10,11,12,13,14
二十三进制:0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,J,K,L(不太清楚,从
16进制推出)本回答被提问者采纳