On Mon, Apr 26, 2010 at 4:05 AM, Vladimir Shevelev <shevelev at bgu.ac.il> wrote: > Thus values of k: 6,9,13,... one can call "non-essential"! Can you continue an interest sequence of > "non-essential" k? I don't think they are really non-essential. That is, if we exclude, say, hexagonal numbers, the whole sequence of records may change. Max