a(n) = Sum_{k=0..n+2} (k+1) * A026323(n, k).

Terms

a(0) =1a(1) =6a(2) =27a(3) =101a(4) =357a(5) =1215a(6) =4043a(7) =13239a(8) =42849a(9) =137446a(10) =437775a(11) =1386369a(12) =4369661a(13) =13717842a(14) =42918903a(15) =133887207a(16) =416601657a(17) =1293386940a(18) =4007492727a(19) =12395015289a(20) =38276340453a(21) =118029405441a(22) =363483388935