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

Terms

a(0) =1a(1) =2a(2) =2a(3) =3a(4) =3a(5) =4a(6) =5a(7) =6a(8) =8a(9) =10a(10) =13a(11) =16a(12) =21a(13) =26a(14) =34a(15) =43a(16) =55a(17) =70a(18) =90a(19) =115a(20) =147a(21) =188a(22) =241a(23) =308a(24) =395a(25) =505a(26) =647a(27) =828a(28) =1061a(29) =1358