Triangular numbers composed of digits {1,2,8}.

Terms

a(0) =1a(1) =21a(2) =28a(3) =1128a(4) =2211a(5) =8128a(6) =118828a(7) =222111a(8) =821121a(9) =828828a(10) =881128a(11) =1188111a(12) =1828828a(13) =22221111a(14) =28218828a(15) =88811128a(16) =1821212128a(17) =2222211111a(18) =8888111128a(19) =222222111111a(20) =888881111128