a(n) = floor(n^(3/2)).

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =8a(5) =11a(6) =14a(7) =18a(8) =22a(9) =27a(10) =31a(11) =36a(12) =41a(13) =46a(14) =52a(15) =58a(16) =64a(17) =70a(18) =76a(19) =82a(20) =89a(21) =96a(22) =103a(23) =110a(24) =117a(25) =125a(26) =132a(27) =140a(28) =148a(29) =156