Factor 2n+1 = (2^m1)*(3^m2)*(5^m3)*...; a(n) = number of initial zero exponents.

Terms

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