a(n) = integer nearest a(n-1)/(sqrt(6) - 2), where a(0) = 1.

Terms

a(0) =1a(1) =2a(2) =4a(3) =9a(4) =20a(5) =44a(6) =98a(7) =218a(8) =485a(9) =1079a(10) =2400a(11) =5339a(12) =11878a(13) =26426a(14) =58791a(15) =130795a(16) =290986a(17) =647370a(18) =1440233a(19) =3204151a(20) =7128419a(21) =15858914a(22) =35282038a(23) =78493533a(24) =174628085a(25) =388502937a(26) =864319917a(27) =1922891303a(28) =4277942565a(29) =9517330782