Least positive integer k for which 4^n divides k!.

Terms

a(0) =1a(1) =4a(2) =6a(3) =8a(4) =10a(5) =12a(6) =16a(7) =16a(8) =18a(9) =20a(10) =24a(11) =24a(12) =28a(13) =30a(14) =32a(15) =32a(16) =34a(17) =36a(18) =40a(19) =40a(20) =44a(21) =46a(22) =48a(23) =48a(24) =52a(25) =54a(26) =56a(27) =58a(28) =60a(29) =64