Least positive integer k for which 3^n divides k!.

Terms

a(0) =1a(1) =3a(2) =6a(3) =9a(4) =9a(5) =12a(6) =15a(7) =18a(8) =18a(9) =21a(10) =24a(11) =27a(12) =27a(13) =27a(14) =30a(15) =33a(16) =36a(17) =36a(18) =39a(19) =42a(20) =45a(21) =45a(22) =48a(23) =51a(24) =54a(25) =54a(26) =54a(27) =57a(28) =60a(29) =63