Numbers k such that the k-th triangular number contains only digits {1,3,5}.

Terms

a(0) =1a(1) =2a(2) =5a(3) =10a(4) =17a(5) =26a(6) =101a(7) =257a(8) =266a(9) =2657a(10) =2666a(11) =8382a(12) =10114a(13) =10130a(14) =26657a(15) =26666a(16) =55733a(17) =101342a(18) =103453a(19) =176257a(20) =266657a(21) =266666a(22) =553778a(23) =557342a(24) =794142a(25) =843010a(26) =1645085a(27) =2666657a(28) =2666666a(29) =3209770