Numbers k such that the k-th triangular number contains only digits {7,8,9}.

A119237

Numbers k such that the k-th triangular number contains only digits {7,8,9}.

Terms

    a(0) =12a(1) =132a(2) =1332a(3) =13332a(4) =133332a(5) =1247307a(6) =1333332a(7) =3949427a(8) =13333332a(9) =133333332a(10) =1333333332a(11) =13333333332a(12) =133333333332a(13) =397189873707

External references