Powers of sqrt(7) rounded down.

Terms

a(0) =1a(1) =2a(2) =7a(3) =18a(4) =49a(5) =129a(6) =343a(7) =907a(8) =2401a(9) =6352a(10) =16807a(11) =44467a(12) =117649a(13) =311269a(14) =823543a(15) =2178889a(16) =5764801a(17) =15252229a(18) =40353607a(19) =106765608a(20) =282475249a(21) =747359260a(22) =1977326743a(23) =5231514822a(24) =13841287201a(25) =36620603758