510x101 1.0X1070/ 2,0x/0-3 ~ 2,5 x 105 t₁² 2.4² +3·4² +4.4ª +in+ n.4″+ (nel) 4^ ghti 2.4043, 44 troethe -14 tn= ~3 t n = 2₁4²³² + √√·43 + ligt fleit tightlights - (nti) qhtz 4 和 初項64,公比4項数n → N-1 3=ntl 4 4² '+ (ner) fitz 64(4^-17 44 ni n項 3 4²³ +4²+ &² +1.49².