OEIS has three sequences, A019989, A019990, and A019991, entered by Neil Sloane in 1996 but credited to Bill Gosper. The wording is quite terse, but reasonably clear. There is little commentary, and only about 60 terms are given. Recently on Sequence Fanatics, Sean Irvine reported that he tried to reproduce the data from the given definitions and failed. I was skeptical, but then I tried the experiment myself and also failed. Obviously Sean and I are misunderstanding the wording in the same way, and I'd like to reconstruct what was meant. Below, I'm going to give my reconstruction, which must be wrong at some point! I hope somebody (hint, hint) can clear up my misunderstanding. The underlying structure is a set of six boolean sequences, named a, b, c, A, B, C. At n=0, they are initialized with a(0) true, and the rest false. For any future n, the values are calculated from one particular set of six old values, the ones for k = floor((n+1)/3). For example, the value at 117 are calculated from those at 39. The value of each of the sequences at n is derived from the values at k by OR-ing together three of the values at k. The rule is quite symmetrical: the new value for each sequence is derived from the old value of the same sequence, OR-ed together with the values of the two sequences that differ from the given one in both case and letter. For example, B(n) = B(k) OR a(k) OR c(k). The three sequences in OEIS are defined in terms of a(2n), b(2n), and c(2n). A number n is in the list A019989 if a(2n) is true, and the other two sequences are built from b and c respectively. The problem that Sean and I encountered is that, because OR is monotonic, all six sequences seem to be quickly driven to true, and stay there. My reconstruction is as follows: n=0: abc/ABC = TFF/FFF n=1: TFF/FTT n=2, 3, 4: TTT/FTT all n>=5: TTT/TTT Sean tried exclusive OR, and some other options, and it failed in different ways that he did not share. What was the intent here?