[seqfan] Re: Help with A028247 Number of T-frame polyominoes with n cells

[Don Reble]

> I hope that someone will edit the entry and give a precise description,
> and so on.

    While we're at it, here's an observation.
    For 2 <= n <= 28, a(2n) < a(2n+1);
    for 29 <= n <= 99, a(2n) > a(2n+1).
    In a plot with separate trend curves for odds and evens,
    it appears that the latter be true for all large n.
    Divisibility of n/3 may also have an effect.

-- 
Don Reble  djr at nk.ca