Numbers k such that the k-th triangular number contains only digits {0,1,2}.

Terms

a(0) =1a(1) =4a(2) =6a(3) =15a(4) =20a(5) =66a(6) =141a(7) =200a(8) =473a(9) =666a(10) =2000a(11) =6666a(12) =14840a(13) =15620a(14) =20000a(15) =49193a(16) =66666a(17) =154926a(18) =200000a(19) =494006a(20) =666666a(21) =2000000a(22) =4939858a(23) =6666666a(24) =20000000a(25) =66666666a(26) =200000000a(27) =200105073a(28) =651307933a(29) =666666666