Duplicate of A008998.

Terms

a(0) =0a(1) =1a(2) =2a(3) =4a(4) =9a(5) =20a(6) =44a(7) =97a(8) =214a(9) =472a(10) =1041a(11) =2296a(12) =5064a(13) =11169a(14) =24634a(15) =54332