a(n) = least k>1 such that k^n divides k!.

Terms

a(0) =2a(1) =6a(2) =15a(3) =18a(4) =12a(5) =32a(6) =24a(7) =36a(8) =40a(9) =45a(10) =48a(11) =100a(12) =84a(13) =60a(14) =154a(15) =165a(16) =72a(17) =96a(18) =80a(19) =126a(20) =90a(21) =135a(22) =286a(23) =200a(24) =312a(25) =264a(26) =168a(27) =120a(28) =297a(29) =189