a(n) = Sum_{i=0..n} floor((2*i + 2)/(n - i + 1)).

Terms

a(0) =2a(1) =5a(2) =8a(3) =12a(4) =17a(5) =20a(6) =26a(7) =31a(8) =36a(9) =41a(10) =48a(11) =52a(12) =59a(13) =66a(14) =71a(15) =76a(16) =86a(17) =89a(18) =98a(19) =105a(20) =110a(21) =117a(22) =126a(23) =132a(24) =139a(25) =146a(26) =155a(27) =160a(28) =171a(29) =174