a(n) = A047769(2n).

Terms

a(0) =0a(1) =1a(2) =5a(3) =26a(4) =133a(5) =708a(6) =3860a(7) =21604a(8) =123266a(9) =715216a(10) =4206956a(11) =25032840a(12) =150413322a(13) =911379384a(14) =5562367173a(15) =34164355715a(16) =211015212580