Partial sums of A000105.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =10a(5) =22a(6) =57a(7) =165a(8) =534a(9) =1819a(10) =6474a(11) =23547a(12) =87147a(13) =325738a(14) =1227709a(15) =4654285a(16) =17733540a(17) =67841449a(18) =260463501a(19) =1003087733a(20) =3873759683a(21) =14996820361a(22) =58188678049a(23) =226235685777a(24) =881235386180