What is the recursive formula for the sequence? 4, 40, 600, 12000, 300000, ... Oa1 = 4, an = 5nan-1 a1 = 4, an = 5 + nan-1 O al = 4, an = nan-1 Oal = 4, an = n+ 5an-1 O a1 = 4, an = 5an-1 - n