Triangular numbers composed of digits {5,7,8}.

Terms

a(0) =55a(1) =78a(2) =5778a(3) =7875a(4) =8778a(5) =75855a(6) =887778a(7) =7575778a(8) =55888878a(9) =57775875a(10) =87787875a(11) =88877778a(12) =5587777755a(13) =8888777778a(14) =787575878775a(15) =888887777778