Diagonal sum of right-justified array T given by A027023.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =7a(5) =18a(6) =43a(7) =103a(8) =264a(9) =687a(10) =1809a(11) =4836a(12) =13049a(13) =35493a(14) =97218a(15) =267857a(16) =741791a(17) =2063574a(18) =5763595a(19) =16155403a(20) =45429488a(21) =128121191a(22) =362287433a(23) =1026918632a(24) =2917313257a(25) =8304598593a(26) =23685134746a(27) =67669857661a(28) =193652803391