2×1=2 (multiply first term by 1 to get 2nd term)
2×3=6 (multiply 2nd term by (1+2) to get 3rd term)
6×5=30 (multiply 3rd term by (1+2+2) to get 4th term)
30×7=210 (multiply 4th term by (1+2+2+2) to get 5th term)
210×9=1890, 1890×11=20790, 20790×13=270270, 4054050, etc.