a(n) = sigma(lcm(1,2,...,n)) = A000203(A003418(n)).

Terms

a(0) =1a(1) =3a(2) =12a(3) =28a(4) =168a(5) =168a(6) =1344a(7) =2880a(8) =9360a(9) =9360a(10) =112320a(11) =112320a(12) =1572480a(13) =1572480a(14) =1572480a(15) =3249792a(16) =58496256a(17) =58496256a(18) =1169925120a(19) =1169925120a(20) =1169925120a(21) =1169925120a(22) =28078202880a(23) =28078202880a(24) =145070714880a(25) =145070714880