Partial sum of A005915.

Terms

a(0) =1a(1) =15a(2) =72a(3) =220a(4) =525a(5) =1071a(6) =1960a(7) =3312a(8) =5265a(9) =7975a(10) =11616a(11) =16380a(12) =22477a(13) =30135a(14) =39600a(15) =51136a(16) =65025a(17) =81567a(18) =101080a(19) =123900a(20) =150381a(21) =180895a(22) =215832a(23) =255600a(24) =300625a(25) =351351a(26) =408240a(27) =471772a(28) =542445a(29) =620775