a(n) = n * (4^n - 2^n) / Clausen(n, 0).

Terms

a(0) =0a(1) =2a(2) =12a(3) =56a(4) =480a(5) =992a(6) =4032a(7) =16256a(8) =261120a(9) =784896a(10) =1047552a(11) =4192256a(12) =33546240a(13) =67100672a(14) =268419072a(15) =1073709056a(16) =34359214080a(17) =17179738112a(18) =206157643776a(19) =274877382656