a(n) = 2^(n-1) - A190820(n).

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =3a(5) =9a(6) =23a(7) =59a(8) =145a(9) =346a(10) =787a(11) =1770a(12) =3899a(13) =8482a(14) =18337