G.f.: x^2 * f''(x), where f(x) = Product_{k>=1} (1 + x^k).

Terms

a(0) =0a(1) =0a(2) =2a(3) =12a(4) =24a(5) =60a(6) =120a(7) =210a(8) =336a(9) =576a(10) =900a(11) =1320a(12) =1980a(13) =2808a(14) =4004a(15) =5670a(16) =7680a(17) =10336a(18) =14076a(19) =18468a(20) =24320a(21) =31920a(22) =41118a(23) =52624a(24) =67344a(25) =85200a(26) =107250a(27) =134784a(28) =167832a(29) =207872