A005195(n) - A005195(n-2).

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =7a(5) =14a(6) =27a(7) =56a(8) =116a(9) =253a(10) =557a(11) =1272a(12) =2948a(13) =6998a(14) =16856a(15) =41306a(16) =102449a(17) =257294a(18) =652566a(19) =1670679a(20) =4311109a(21) =11206278a(22) =29316294a(23) =77144518a(24) =204072054a(25) =542446974a(26) =1448230644a(27) =3882179984a(28) =10445521740a(29) =28202158173