First differences of A066425.

Terms

a(0) =2a(1) =5a(2) =10a(3) =23a(4) =43a(5) =97a(6) =183a(7) =387a(8) =761a(9) =1525a(10) =3070a(11) =6109a(12) =12331a(13) =24570a(14) =49119a(15) =98308a(16) =196634a(17) =393229a(18) =786794a(19) =1573225