Number of 7's when k is written in base b for all b and k satisfying 2<=b<=n+1, 1<=k<=n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =1a(7) =1a(8) =1a(9) =1a(10) =1a(11) =1a(12) =1a(13) =1a(14) =2a(15) =3a(16) =4a(17) =5a(18) =6a(19) =7a(20) =8a(21) =9a(22) =11a(23) =12a(24) =14a(25) =15a(26) =17a(27) =18a(28) =20a(29) =21