Omit zero digits from factorial numbers.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =12a(6) =72a(7) =54a(8) =432a(9) =36288a(10) =36288a(11) =399168a(12) =47916a(13) =622728a(14) =871782912a(15) =137674368a(16) =2922789888a(17) =35568742896a(18) =64237375728a(19) =121645148832a(20) =243292817664