a(n) = a(n-1) + 2*a(floor(n/2)) if n > 0, otherwise 1.

Terms

a(0) =1a(1) =3a(2) =9a(3) =15a(4) =33a(5) =51a(6) =81a(7) =111a(8) =177a(9) =243a(10) =345a(11) =447a(12) =609a(13) =771a(14) =993a(15) =1215a(16) =1569a(17) =1923a(18) =2409a(19) =2895a(20) =3585a(21) =4275a(22) =5169a(23) =6063a(24) =7281a(25) =8499a(26) =10041a(27) =11583a(28) =13569a(29) =15555