a(1) = a(2) = 1; a(n+1) = round( a(n) + sqrt(3)*a(n-1) ).

Terms

a(0) =1a(1) =1a(2) =3a(3) =5a(4) =10a(5) =19a(6) =36a(7) =69a(8) =131a(9) =251a(10) =478a(11) =913a(12) =1741a(13) =3322a(14) =6338a(15) =12092a(16) =23070a(17) =44014a(18) =83972a(19) =160206a(20) =305650a(21) =583135a(22) =1112536a(23) =2122555a(24) =4049524a(25) =7725897a(26) =14739878a(27) =28121524a(28) =53651742a(29) =102359650