Column 2 of triangle A055907.

Terms

a(0) =1a(1) =4a(2) =10a(3) =21a(4) =39a(5) =67a(6) =107a(7) =163a(8) =238a(9) =337a(10) =463a(11) =622a(12) =818a(13) =1058a(14) =1346a(15) =1690a(16) =2095a(17) =2570a(18) =3120a(19) =3755a(20) =4481a(21) =5309a(22) =6245a(23) =7301a(24) =8484a(25) =9807a(26) =11277a(27) =12908a(28) =14708a(29) =16692