a(n) = A170907(2^n).

Terms

a(0) =1a(1) =4a(2) =13a(3) =47a(4) =176a(5) =678a(6) =2658a(7) =10521a(8) =41860a(9) =166995a(10) =667100a(11) =2666651a(12) =10663099a(13) =42645332