Diagonal sums of Riordan array ((1-2x)/(1 - 3x + x^2),x(1-x)/(1 - 3x + x^2)).

Terms

a(0) =1a(1) =1a(2) =3a(3) =8a(4) =23a(5) =66a(6) =190a(7) =547a(8) =1575a(9) =4535a(10) =13058a(11) =37599a(12) =108262a(13) =311728a(14) =897585a(15) =2584493a(16) =7441751a(17) =21427668a(18) =61698511a(19) =177653782a(20) =511533678a(21) =1472902523a(22) =4241053787a(23) =12211627683a(24) =35161980526a(25) =101244887791a(26) =291523035690a(27) =839407126544