a(n) = Sum_{k=1..n^2} d(k), d(k) = number of divisors of k (A000005).

Terms

a(0) =1a(1) =8a(2) =23a(3) =50a(4) =87a(5) =140a(6) =201a(7) =280a(8) =373a(9) =482a(10) =605a(11) =746a(12) =897a(13) =1070a(14) =1261a(15) =1466a(16) =1689a(17) =1932a(18) =2189a(19) =2468a(20) =2761a(21) =3074a(22) =3405a(23) =3764a(24) =4127a(25) =4518a(26) =4925a(27) =5360a(28) =5807a(29) =6276