a(n) = integer nearest n*(1+sqrt(2)).

Terms

a(0) =2a(1) =5a(2) =7a(3) =10a(4) =12a(5) =14a(6) =17a(7) =19a(8) =22a(9) =24a(10) =27a(11) =29a(12) =31a(13) =34a(14) =36a(15) =39a(16) =41a(17) =43a(18) =46a(19) =48a(20) =51a(21) =53a(22) =56a(23) =58a(24) =60a(25) =63a(26) =65a(27) =68a(28) =70a(29) =72