Triangular numbers composed of digits {1,8,9}.

Terms

a(0) =1a(1) =91a(2) =1891a(3) =8911a(4) =188191a(5) =889111a(6) =899811a(7) =998991a(8) =1188111a(9) =11899881a(10) =88891111a(11) =1918188891a(12) =8888911111a(13) =9998888991a(14) =189889118191a(15) =191819818191a(16) =199198198891a(17) =888889111111