a(n) = n * Sum_{d|n} binomial(d+2,3)/d.

Terms

a(0) =1a(1) =6a(2) =13a(3) =32a(4) =40a(5) =94a(6) =91a(7) =184a(8) =204a(9) =320a(10) =297a(11) =612a(12) =468a(13) =770a(14) =850a(15) =1184a(16) =986a(17) =1752a(18) =1349a(19) =2280a(20) =2114a(21) =2662a(22) =2323a(23) =4184a(24) =3125a(25) =4264a(26) =4266a(27) =5740a(28) =4524a(29) =7660