a(n) = 1*2*3*4 + 5*6*7*8 + 9*10*11*12 + 13*14*15*16 + 17*18*19*20 + ... + (up to n).

Terms

a(0) =1a(1) =2a(2) =6a(3) =24a(4) =29a(5) =54a(6) =234a(7) =1704a(8) =1713a(9) =1794a(10) =2694a(11) =13584a(12) =13597a(13) =13766a(14) =16314a(15) =57264a(16) =57281a(17) =57570a(18) =63078a(19) =173544a(20) =173565a(21) =174006a(22) =184170a(23) =428568a(24) =428593a(25) =429218a(26) =446118a(27) =919968a(28) =919997a(29) =920838