Diagonal sums of the Riordan matrix (1/(1-3*x^2),x/(1-x)) (A191582).

Terms

a(0) =1a(1) =0a(2) =4a(3) =1a(4) =14a(5) =6a(6) =47a(7) =26a(8) =154a(9) =99a(10) =496a(11) =352a(12) =1577a(13) =1200a(14) =4964a(15) =3977a(16) =15502a(17) =12918a(18) =48103a(19) =41338a(20) =148490a(21) =130779a(22) =456416a(23) =410048a(24) =1397905a(25) =1276512a(26) =4268740a(27) =3950929a(28) =13002638a(29) =12170598