a(n) = n*(2^(n-1) - n - 1).

Terms

a(0) =0a(1) =12a(2) =50a(3) =150a(4) =392a(5) =952a(6) =2214a(7) =5010a(8) =11132a(9) =24420a(10) =53066a(11) =114478a(12) =245520a(13) =524016a(14) =1113806a(15) =2358954a(16) =4980356a(17) =10485340a(18) =22019634a(19) =46136838a(20) =96468440a(21) =201325992a(22) =419429750a(23) =872414530a(24) =1811938572a(25) =3758095572a(26) =7784627354a(27) =16106126430a(28) =33285995552a(29) =68719475680