a(n) = least k>0 such that n! divides Fibonacci(k).

Terms

a(0) =1a(1) =1a(2) =3a(3) =12a(4) =12a(5) =60a(6) =60a(7) =120a(8) =480a(9) =4320a(10) =43200a(11) =43200a(12) =518400a(13) =3628800a(14) =7257600a(15) =108864000a(16) =1741824000a(17) =1741824000a(18) =31352832000a(19) =31352832000a(20) =627056640000