a(n) = Sum {k + j*m <= n} (k + j*m), with 0 < k,j,m <= n.

Terms

a(0) =0a(1) =0a(2) =2a(3) =11a(4) =31a(5) =71a(6) =131a(7) =229a(8) =357a(9) =537a(10) =767a(11) =1064a(12) =1412a(13) =1867a(14) =2385a(15) =3000a(16) =3720a(17) =4570a(18) =5506a(19) =6608a(20) =7808a(21) =9194a(22) =10734a(23) =12436a(24) =14260a(25) =16360a(26) =18622a(27) =21079a(28) =23739a(29) =26668