a(n) = A152800(n+2,2n+1) for n>=0.

Terms

a(0) =1a(1) =3a(2) =10a(3) =41a(4) =172a(5) =749a(6) =3332a(7) =15041a(8) =68640a(9) =315840a(10) =1462798a(11) =6810588a(12) =31846811a(13) =149459541a(14) =703592472a(15) =3321019270a(16) =15711717162a(17) =74482623635a(18) =353723268817