a(n) = n* - 2^(n-1), where n* (A003418) = least common multiple of the numbers [1,...,n].

Terms

a(0) =0a(1) =0a(2) =2a(3) =4a(4) =44a(5) =28a(6) =356a(7) =712a(8) =2264a(9) =2008a(10) =26696a(11) =25672a(12) =356264a(13) =352168a(14) =343976a(15) =687952a(16) =12186704a(17) =12121168a(18) =232530416a(19) =232268272a(20) =231743984a(21) =230695408a(22) =5350034576a(23) =5345840272a(24) =26754367184a(25) =26737589968a(26) =80246324336a(27) =80179215472