Numbers k such that the k-th triangular number contains only digits {1,4,5}.

Terms

a(0) =1a(1) =5a(2) =9a(3) =10a(4) =101a(5) =298a(6) =301a(7) =1761a(8) =10113a(9) =10114a(10) =15133a(11) =91010a(12) =297134a(13) =3329010a(14) =10406301a(15) =15133698a(16) =30180826a(17) =47989885a(18) =101434130a(19) =301468258a(20) =942805541a(21) =9544151561a(22) =16977369885a(23) =95335633898