a(n) = diagonal sum of left-justified array T given by A027052.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =4a(6) =5a(7) =7a(8) =11a(9) =14a(10) =22a(11) =32a(12) =43a(13) =67a(14) =97a(15) =134a(16) =206a(17) =298a(18) =419a(19) =637a(20) =923a(21) =1312a(22) =1978a(23) =2872a(24) =4111a(25) =6161a(26) =8961a(27) =12888a(28) =19232a(29) =28010