a(n) = OrdinaryUnitarySigma(a(n-1)).

Terms

a(0) =2a(1) =3a(2) =4a(3) =7a(4) =8a(5) =15a(6) =24a(7) =60a(8) =168a(9) =480a(10) =1512a(11) =3360a(12) =12096a(13) =28448a(14) =64512a(15) =163760a(16) =401760a(17) =991872a(18) =2399040a(19) =6858000a(20) =13999104a(21) =32752000a(22) =69400800a(23) =172186560a(24) =517867392a(25) =1666990080a(26) =5662137600a(27) =14475575296a(28) =33946612000a(29) =73359820800