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

Terms

a(0) =4a(1) =12a(2) =24a(3) =24a(4) =32a(5) =80a(6) =360a(7) =1704a(8) =1716a(9) =1836a(10) =3024a(11) =13584a(12) =13600a(13) =13824a(14) =16944a(15) =57264a(16) =57284a(17) =57644a(18) =64104a(19) =173544a(20) =173568a(21) =174096a(22) =185688a(23) =428568a(24) =428596a(25) =429324a(26) =448224a(27) =919968a(28) =920000a(29) =920960