a(0)=1, a(1)=3, a(n) = floor((Pi + 1/Pi)*a(n-1) - a(n-2)).

Terms

a(0) =1a(1) =3a(2) =9a(3) =28a(4) =87a(5) =273a(6) =857a(7) =2692a(8) =8457a(9) =26568a(10) =83465a(11) =262212a(12) =823762a(13) =2587924a(14) =8130202a(15) =25541782a(16) =80241874a(17) =252087281a(18) =791955549a(19) =2488001734a(20) =7816287969a(21) =24555592861a(22) =77143670136a(23) =242353987370a(24) =761377506289