A007318 * A131055.

Terms

a(0) =1a(1) =3a(2) =7a(3) =17a(4) =41a(5) =97a(6) =225a(7) =513a(8) =1153a(9) =2561a(10) =5633a(11) =12289a(12) =26625a(13) =57345a(14) =122881a(15) =262145a(16) =557057a(17) =1179649a(18) =2490369a(19) =5242881a(20) =11010049a(21) =23068673a(22) =48234497a(23) =100663297a(24) =209715201a(25) =436207617a(26) =905969665