T(n,1) + T(n,2) + ... T(n,n), where T is the array in A026098.

Terms

a(0) =1a(1) =5a(2) =15a(3) =34a(4) =68a(5) =118a(6) =186a(7) =279a(8) =400a(9) =563a(10) =754a(11) =998a(12) =1265a(13) =1614a(14) =2015a(15) =2468a(16) =3023a(17) =3610a(18) =4277a(19) =4980a(20) =5795a(21) =6734a(22) =7754a(23) =8847a(24) =10170a(25) =11502a(26) =13002a(27) =14661a(28) =16373a(29) =18150