a(n) = floor(4^n/(2 + sqrt(2))^n).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =2a(7) =3a(8) =3a(9) =4a(10) =4a(11) =5a(12) =6a(13) =7a(14) =9a(15) =10a(16) =12a(17) =14a(18) =17a(19) =20a(20) =23a(21) =27a(22) =32a(23) =38a(24) =44a(25) =52a(26) =61a(27) =71a(28) =84a(29) =98