Powers of sqrt(7) rounded up.

Terms

a(0) =1a(1) =3a(2) =7a(3) =19a(4) =49a(5) =130a(6) =343a(7) =908a(8) =2401a(9) =6353a(10) =16807a(11) =44468a(12) =117649a(13) =311270a(14) =823543a(15) =2178890a(16) =5764801a(17) =15252230a(18) =40353607a(19) =106765609a(20) =282475249a(21) =747359261a(22) =1977326743a(23) =5231514823a(24) =13841287201a(25) =36620603759