a(n) = (1/8)*A291387(n).

Terms

a(0) =1a(1) =7a(2) =44a(3) =262a(4) =1504a(5) =8416a(6) =46208a(7) =250016a(8) =1337088a(9) =7083264a(10) =37229568a(11) =194383360a(12) =1009172480a(13) =5213634560a(14) =26819756032a(15) =137445318656a(16) =702021435392