a(n) = T(2n,n-1), where T is the array in A026268.

Terms

a(0) =1a(1) =3a(2) =14a(3) =72a(4) =385a(5) =2110a(6) =11757a(7) =66298a(8) =377245a(9) =2161771a(10) =12458186a(11) =72130114a(12) =419239101a(13) =2444741300a(14) =14296415880a(15) =83807317674a(16) =492339686501