Partial sums of A050405.

Terms

a(0) =1a(1) =16a(2) =100a(3) =408a(4) =1290a(5) =3432a(6) =8052a(7) =17160a(8) =33891a(9) =62920a(10) =110968a(11) =187408a(12) =304980a(13) =480624a(14) =736440a(15) =1100784a(16) =1609509a(17) =2307360a(18) =3249532a(19) =4503400a(20) =6150430a(21) =8288280a(22) =11033100a(23) =14522040a(24) =18915975