a(n) = floor( a(n-1)/(sqrt(2) - 1) ), with a(0) = 1.

Terms

a(0) =1a(1) =2a(2) =4a(3) =9a(4) =21a(5) =50a(6) =120a(7) =289a(8) =697a(9) =1682a(10) =4060a(11) =9801a(12) =23661a(13) =57122a(14) =137904a(15) =332929a(16) =803761a(17) =1940450a(18) =4684660a(19) =11309769a(20) =27304197a(21) =65918162a(22) =159140520a(23) =384199201a(24) =927538921a(25) =2239277042a(26) =5406093004a(27) =13051463049a(28) =31509019101a(29) =76069501250