3-magic series constant.

Terms

a(0) =1a(1) =50a(2) =675a(3) =4624a(4) =21125a(5) =73926a(6) =214375a(7) =540800a(8) =1225449a(9) =2550250a(10) =4952651a(11) =9082800a(12) =15873325a(13) =26622974a(14) =43095375a(15) =67634176a(16) =103295825a(17) =154001250a(18) =224707699a(19) =321602000a(20) =452316501a(21) =626168950a(22) =854427575a(23) =1150602624