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

Terms

a(0) =0a(1) =2a(2) =6a(3) =15a(4) =36a(5) =85a(6) =198a(7) =455a(8) =1032a(9) =2313a(10) =5130a(11) =11275a(12) =24588a(13) =53261a(14) =114702a(15) =245775a(16) =524304a(17) =1114129a(18) =2359314a(19) =4980755a(20) =10485780a(21) =22020117a(22) =46137366a(23) =96469015a(24) =201326616a(25) =419430425a(26) =872415258a(27) =1811939355a(28) =3758096412a(29) =7784628253