Partial sums of sequence (essentially A002378): 1, 2, 6, 12, 20, 30, 42, 56, 72, 90, ...

Terms

a(0) =1a(1) =3a(2) =9a(3) =21a(4) =41a(5) =71a(6) =113a(7) =169a(8) =241a(9) =331a(10) =441a(11) =573a(12) =729a(13) =911a(14) =1121a(15) =1361a(16) =1633a(17) =1939a(18) =2281a(19) =2661a(20) =3081a(21) =3543a(22) =4049a(23) =4601a(24) =5201a(25) =5851a(26) =6553a(27) =7309a(28) =8121a(29) =8991