Exponent of 7 (value of j) in n-th number of form 3^i*7^j.

Terms

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