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

Terms

a(0) =2a(1) =14a(2) =79a(3) =446a(4) =2530a(5) =14442a(6) =82913a(7) =478384a(8) =2771900a(9) =16119808a(10) =94038087a(11) =550083340a(12) =3225409094a(13) =18951732050a(14) =111562247565a(15) =657813211278