Numbers k such that the k-th triangular number contains only digits {0,1,5}.

Terms

a(0) =1a(1) =4a(2) =5a(3) =10a(4) =14a(5) =100a(6) =101a(7) =141a(8) =173a(9) =458a(10) =1000a(11) =1001a(12) =1005a(13) =1010a(14) =4475a(15) =10000a(16) =10001a(17) =10005a(18) =10010a(19) =10100a(20) =10110a(21) =10114a(22) =14869a(23) =45858a(24) =54873a(25) =100000a(26) =100001a(27) =100005a(28) =100010a(29) =100100