Numbers k such that the k-th triangular number contains only digits {4,7,8}.

A119217

Numbers k such that the k-th triangular number contains only digits {4,7,8}.

Terms

    a(0) =12a(1) =132a(2) =947a(3) =1332a(4) =3867a(5) =13332a(6) =133332a(7) =299492a(8) =1222692a(9) =1333332a(10) =13333332a(11) =133333332a(12) =1333333332a(13) =3944306652a(14) =13333333332a(15) =122020365307a(16) =133333333332a(17) =394329425347a(18) =988724307827

External references