a(n) = Sum_{k=0..n} (k+1) * A026681(n, k).

Terms

a(0) =1a(1) =3a(2) =10a(3) =30a(4) =78a(5) =189a(6) =480a(7) =1242a(8) =3030a(9) =7084a(10) =17112a(11) =42146a(12) =99792a(13) =229065a(14) =540544a(15) =1298851a(16) =3025386a(17) =6871084a(18) =15993500a(19) =37857267a(20) =87275980a(21) =196867143a(22) =454118616a(23) =1064055225a(24) =2435780334a(25) =5468505723a(26) =12533827796a(27) =29153115186