a(n) = Sum_{k >=1} floor(n*sqrt(2)^(3-k)).

Terms

a(0) =3a(1) =9a(2) =16a(3) =22a(4) =28a(5) =36a(6) =40a(7) =49a(8) =55a(9) =62a(10) =66a(11) =76a(12) =82a(13) =87a(14) =94a(15) =103a(16) =111a(17) =116a(18) =121a(19) =130a(20) =134a(21) =141a(22) =150a(23) =157a(24) =163a(25) =170a(26) =176a(27) =182a(28) =190a(29) =196