a(n) = n*(2^n - n + 1) + 2^(n-1)*(n^2 - 3*n + 2).

Terms

a(0) =2a(1) =6a(2) =26a(3) =100a(4) =332a(5) =994a(6) =2774a(7) =7368a(8) =18872a(9) =47014a(10) =114578a(11) =274300a(12) =647012a(13) =1507146a(14) =3473198a(15) =7929616a(16) =17956592a(17) =40369870a(18) =90177194a(19) =200277636a(20) =442498652a(21) =973078066a(22) =2130705926a(23) =4647288280a(24) =10099883432a(25) =21877489014a(26) =47244639554a(27) =101737037068