Numbers k such that the k-th triangular number contains only digits {0,1,8}.

Terms

a(0) =1a(1) =4a(2) =46a(3) =126a(4) =141a(5) =404a(6) =466a(7) =1541a(8) =4004a(9) =4195a(10) =4666a(11) =12658a(12) =13266a(13) =40004a(14) =41995a(15) =46666a(16) =147024a(17) =400004a(18) =402760a(19) =466666a(20) =1272798a(21) =1327266a(22) =1332666a(23) =4000004a(24) =4666666a(25) =40000004a(26) =46666666a(27) =133272666a(28) =133326666a(29) =148329375