a(n) = 1*2*3*4*5*6 + 7*8*9*10*11*12 + 13*14*15*16*17*18 + ... + (up to n).

Terms

a(0) =1a(1) =2a(2) =6a(3) =24a(4) =120a(5) =720a(6) =727a(7) =776a(8) =1224a(9) =5760a(10) =56160a(11) =666000a(12) =666013a(13) =666182a(14) =668730a(15) =709680a(16) =1408560a(17) =14032080a(18) =14032099a(19) =14032460a(20) =14040060a(21) =14207640a(22) =18069960a(23) =110941200a(24) =110941225a(25) =110941850a(26) =110958750a(27) =111432600a(28) =125191800a(29) =538459200