a(n) = Sum_{k=0..n} (k+1) * A026758(n, k).

Terms

a(0) =1a(1) =3a(2) =8a(3) =22a(4) =53a(5) =138a(6) =317a(7) =803a(8) =1794a(9) =4478a(10) =9823a(11) =24321a(12) =52662a(13) =129815a(14) =278365a(15) =684689a(16) =1457113a(17) =3581074a(18) =7574863a(19) =18616678a(20) =39182980a(21) =96351078a(22) =201947877a(23) =497006898a(24) =1038017513a(25) =2557192089a(26) =5324505911a(27) =13131212951a(28) =27268815916