Cumulative sum of triple factorial numbers a(n) = n!!! (A007661).

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =11a(5) =21a(6) =39a(7) =67a(8) =147a(9) =309a(10) =589a(11) =1469a(12) =3413a(13) =7053a(14) =19373a(15) =48533a(16) =106773a(17) =316213a(18) =841093a(19) =1947653a(20) =6136453a(21) =17158933a(22) =41503253a(23) =137845653a(24) =402385173a(25) =1010993173a(26) =3515895573a(27) =10658462613a(28) =27699486613a(29) =100341656213