a(n) = (1/n!)*A001688(n).

Terms

a(0) =9a(1) =53a(2) =181a(3) =465a(4) =1001a(5) =1909a(6) =3333a(7) =5441a(8) =8425a(9) =12501a(10) =17909a(11) =24913a(12) =33801a(13) =44885a(14) =58501a(15) =75009a(16) =94793a(17) =118261a(18) =145845a(19) =178001a(20) =215209a(21) =257973a(22) =306821a(23) =362305a(24) =425001a(25) =495509a(26) =574453a(27) =662481a(28) =760265a(29) =868501