Least k such that decimal representation of k*n contains only digits 0 and 7.

Terms

a(0) =7a(1) =35a(2) =259a(3) =175a(4) =14a(5) =1295a(6) =1a(7) =875a(8) =86419753a(9) =7a(10) =7a(11) =6475a(12) =539a(13) =5a(14) =518a(15) =4375a(16) =4571a(17) =432098765a(18) =4053a(19) =35a(20) =37a(21) =35a(22) =33509a(23) =32375a(24) =28a(25) =2695a(26) =285473251a(27) =25a(28) =265783a(29) =259