a(n) = (1/8)*A290915(n).

Terms

a(0) =0a(1) =1a(2) =4a(3) =18a(4) =84a(5) =387a(6) =1784a(7) =8228a(8) =37944a(9) =174981a(10) =806940a(11) =3721270a(12) =17160940a(13) =79139079a(14) =364956336a(15) =1683025992a(16) =7761412016a(17) =35792386313a(18) =165059516916a(19) =761185462362