Number of 7's when n is written in base b for 2<=b<=n+1.

Terms

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