a(n) = Sum_{k=0..2n} (k+1) * A026519(n, k).

Terms

a(0) =1a(1) =6a(2) =18a(3) =72a(4) =180a(5) =648a(6) =1512a(7) =5184a(8) =11664a(9) =38880a(10) =85536a(11) =279936a(12) =606528a(13) =1959552a(14) =4199040a(15) =13436928a(16) =28553472a(17) =90699264a(18) =191476224a(19) =604661760a(20) =1269789696a(21) =3990767616a(22) =8344332288a(23) =26121388032a(24) =54419558400a(25) =169789022208