a(n) = sum of modular offsets: mod[n+c,b]-(mod[n,b]+c) for c<=b<=n.

Terms

a(0) =1a(1) =3a(2) =8a(3) =13a(4) =27a(5) =34a(6) =61a(7) =76a(8) =111a(9) =136a(10) =201a(11) =213a(12) =303a(13) =354a(14) =439a(15) =490a(16) =642a(17) =682a(18) =871a(19) =935a(20) =1107a(21) =1234a(22) =1509a(23) =1535a(24) =1834a(25) =2011a(26) =2298a(27) =2438a(28) =2872a(29) =2937