a(n) = floor( Gamma(n+1/4) ).

Terms

a(0) =3a(1) =0a(2) =1a(3) =2a(4) =8a(5) =35a(6) =184a(7) =1155a(8) =8376a(9) =69106a(10) =639232a(11) =6552134a(12) =73711509a(13) =902965985a(14) =11964299312a(15) =170491265198