Triangular numbers composed of digits {2,7,8}.

Terms

a(0) =28a(1) =78a(2) =2278a(3) =8778a(4) =222778a(5) =828828a(6) =887778a(7) =8272278a(8) =22227778a(9) =88278828a(10) =88877778a(11) =2222277778a(12) =2882872278a(13) =8882778828a(14) =8888777778a(15) =222222777778a(16) =888827778828a(17) =888887777778