a(n) = n*(n^5 + 1)/2.

Terms

a(0) =0a(1) =1a(2) =33a(3) =366a(4) =2050a(5) =7815a(6) =23331a(7) =58828a(8) =131076a(9) =265725a(10) =500005a(11) =885786a(12) =1492998a(13) =2413411a(14) =3764775a(15) =5695320a(16) =8388616a(17) =12068793a(18) =17006121a(19) =23522950a(20) =32000010a(21) =42883071a(22) =56689963a(23) =74017956a(24) =95551500a(25) =122070325a(26) =154457901a(27) =193710258a(28) =240945166a(29) =297411675