a(n) = diagonal sum of left justified array T given by A027113.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =4a(5) =8a(6) =11a(7) =15a(8) =24a(9) =35a(10) =48a(11) =75a(12) =108a(13) =152a(14) =232a(15) =336a(16) =477a(17) =721a(18) =1046a(19) =1496a(20) =2245a(21) =3264a(22) =4690a(23) =7006a(24) =10200a(25) =14709a(26) =21897a(27) =31916a(28) =46148a(29) =68523