Central terms of triangle A120898 (cascadence of 1+2x+x^2).

Terms

a(0) =1a(1) =1a(2) =5a(3) =14a(4) =43a(5) =156a(6) =535a(7) =1956a(8) =7175a(9) =26418a(10) =98375a(11) =367176a(12) =1378022a(13) =5193625a(14) =19641164a(15) =74535167a(16) =283651169a(17) =1082274210a(18) =4139129734a(19) =15863315213a(20) =60913982404a(21) =234317240601a(22) =902804442380