a(n) = 1*T(n,2n) + 2*T(n,2n-1) + ... + (2n+1)*T(n,0), T given by A027926.

Terms

a(0) =1a(1) =6a(2) =20a(3) =54a(4) =132a(5) =306a(6) =688a(7) =1518a(8) =3308a(9) =7146a(10) =15336a(11) =32742a(12) =69604a(13) =147426a(14) =311264a(15) =655326a(16) =1376220a(17) =2883546a(18) =6029272a(19) =12582870a(20) =26214356a(21) =54525906a(22) =113246160a(23) =234880974a(24) =486539212a(25) =1006632906a(26) =2080374728a(27) =4294967238