a(n) = 2^(n - 2)*(binomial(n,2) + 2).

Terms

a(0) =1a(1) =3a(2) =10a(3) =32a(4) =96a(5) =272a(6) =736a(7) =1920a(8) =4864a(9) =12032a(10) =29184a(11) =69632a(12) =163840a(13) =380928a(14) =876544a(15) =1998848a(16) =4521984a(17) =10158080a(18) =22675456a(19) =50331648a(20) =111149056a(21) =244318208a(22) =534773760a(23) =1166016512a(24) =2533359616a(25) =5486149632a(26) =11844714496a(27) =25501368320a(28) =54760833024a(29) =117306294272