a(n)=(1+2^(1/3))^n.

Terms

a(0) =1a(1) =2a(2) =5a(3) =12a(4) =26a(5) =59a(6) =133a(7) =301a(8) =680a(9) =1538a(10) =3475a(11) =7853a(12) =17747a(13) =40106a(14) =90637a(15) =204833a(16) =462905a(17) =1046130a(18) =2364171a(19) =5342839a(20) =12074394a(21) =27287177a(22) =61666867a(23) =139362250a(24) =314947683a(25) =711756898a(26) =1608514395a(27) =3635115540a(28) =8215074129