a(n) = floor(2^n/(n^2)).

Terms

a(0) =2a(1) =1a(2) =0a(3) =1a(4) =1a(5) =1a(6) =2a(7) =4a(8) =6a(9) =10a(10) =16a(11) =28a(12) =48a(13) =83a(14) =145a(15) =256a(16) =453a(17) =809a(18) =1452a(19) =2621a(20) =4755a(21) =8665a(22) =15857a(23) =29127a(24) =53687a(25) =99273a(26) =184112a(27) =342392a(28) =638372a(29) =1193046