a(n) = Sum_{k=0..2n} (k+1) * A026552(n, k).

Terms

a(0) =1a(1) =6a(2) =27a(3) =72a(4) =270a(5) =648a(6) =2268a(7) =5184a(8) =17496a(9) =38880a(10) =128304a(11) =279936a(12) =909792a(13) =1959552a(14) =6298560a(15) =13436928a(16) =42830208a(17) =90699264a(18) =287214336a(19) =604661760a(20) =1904684544a(21) =3990767616a(22) =12516498432a(23) =26121388032a(24) =81629337600a(25) =169789022208