Triangular numbers composed of digits {0,1,5}.

Terms

a(0) =1a(1) =10a(2) =15a(3) =55a(4) =105a(5) =5050a(6) =5151a(7) =10011a(8) =15051a(9) =105111a(10) =500500a(11) =501501a(12) =505515a(13) =510555a(14) =10015050a(15) =50005000a(16) =50015001a(17) =50055015a(18) =50105055a(19) =51010050a(20) =51111105a(21) =51151555a(22) =110551015a(23) =1051501011a(24) =1505550501a(25) =5000050000a(26) =5000150001a(27) =5000550015a(28) =5001050055a(29) =5010055050