a(n) = A027011(2n+1, n+4).

Terms

a(0) =1a(1) =11a(2) =267a(3) =2620a(4) =16305a(5) =77040a(6) =303553a(7) =1055231a(8) =3358268a(9) =10039132a(10) =28714818a(11) =79649852a(12) =216360858a(13) =579601543a(14) =1538746237a(15) =4061993928a(16) =10685640859a(17) =28051744332a(18) =73551897971a(19) =192720956939a(20) =504774508726