A084175 interleaved with 2*A084175.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =3a(5) =6a(6) =15a(7) =30a(8) =55a(9) =110a(10) =231a(11) =462a(12) =903a(13) =1806a(14) =3655a(15) =7310a(16) =14535a(17) =29070a(18) =58311a(19) =116622a(20) =232903a(21) =465806a(22) =932295a(23) =1864590a(24) =3727815a(25) =7455630a(26) =14913991a(27) =29827982a(28) =59650503a(29) =119301006