a(n) = Sum_{k=0..n} (k+1) * T(n,k), with T given by A026386.

Terms

a(0) =1a(1) =3a(2) =8a(3) =25a(4) =60a(5) =175a(6) =400a(7) =1125a(8) =2500a(9) =6875a(10) =15000a(11) =40625a(12) =87500a(13) =234375a(14) =500000a(15) =1328125a(16) =2812500a(17) =7421875a(18) =15625000a(19) =41015625a(20) =85937500a(21) =224609375a(22) =468750000a(23) =1220703125a(24) =2539062500a(25) =6591796875a(26) =13671875000a(27) =35400390625