Shifts left when Euler transform applied 3 times.

Terms

a(0) =0a(1) =1a(2) =1a(3) =4a(4) =13a(5) =51a(6) =197a(7) =828a(8) =3526a(9) =15538a(10) =69627a(11) =317564a(12) =1466868a(13) =6853320a(14) =32317354a(15) =153636769a(16) =735493374a(17) =3542610091a(18) =17155811156a(19) =83480667707a(20) =407969449010