做这道题要先熟悉质数列和合数列质数列：2,3,5,7,11,13,17,19,23,29,31,37,39……合数列：4,6,8,9,10,12,14,15,16,18,20,22,24……后项减前一项等于合数列,12 16 22 30 39 49 【61】--作差,有4 6 8 9 10 12 ---合数...