To Math-Fun, Seq-Fans: There is an article by Arnold which has appeared in several places. There are two versions in English: MR2080045 Arnold, V. I. From Hilbert's superposition problem to dynamical systems [ MR1733564 (2001h:01031)]. Amer. Math. Monthly 111 (2004), no. 7, 608--624. 01A65 (01A60 37-03 54H20) MR1733564 (2001h:01031) Arnold, V. I. From Hilbert's superposition problem to dynamical systems. The Arnoldfest (Toronto, ON, 1997), 1--18, Fields Inst. Commun., 24, Amer. Math. Soc., Providence, RI, 1999. (Reviewer: Stanis\l aw Janeczko) 01A65 (01A60 37-03 54H20) Footnote 2 says: "Starting from degree 9, one can kill one more coefficient. The known possibilities to kill more coefficients occur along a rather strange infinite sequence of degrees." He is refering to the problem of putting a polynomial equation f(X)=0 into canonical form. E.g. any 5th degree equation can be reduced to x^5 + aX + 1 = 0. My question is, what is this "strange infinite sequence of degrees"? Thanks Neil Sloane