A143105 Let g_0(x,y)=x, g_1(x,y)=x^3+3xy and g_{n+2}(x,y) = (x^2+2y)g_{n+1}(x+y)-y^2g_n(x,y). The entries of the sequence are those odd d for which g_d(x,y) and cx^jy^kg_m(x,y) have at least two terms in common (same coefficients) for some c > 0 and integers j,k and such that g_d(x,y) + cx^jy^k(1+y^m - g_m(x,y)) has all positive coefficients.

1, 3, 5, 9, 17, 21, 33, 41, 45, 53, 69, 77, 81, 93, 105, 113, 117, 125, 129, 141, 149, 153, 161, 165, 177, 185, 201, 213, 221, 225, 249, 261, 269, 273, 285, 297, 305, 309, 333, 341, 345, 357, 365, 369, 381, 405, 413, 417, 429, 437, 441, 453, 465, 473, 489, 501

Offset: 0

Author

Jiri Lebl (jlebl(AT)math.uiuc.edu), Jul 25 2008

Keywords

• nonn

Comments

Note that g_k(x,y) always has positive coefficients. The sequence are degrees for which a certain construction (see paper by D'Angelo-Lebl) of proper monomial holomorphic mappings of balls does not give new noninvariant monomial mappings.

It is unknown if this sequence is infinite (conjectured to be so). Furthermore A143106 is definitely a subsequence of this sequence, but it is unknown if the two are in fact equal.

Examples

			For example when d=7, we get the following new polynomials x^7 + 7/2 xy + 7/2 x^5y 7/2 xy^5 and x^7 + 7 x^3y + 7 xy^3 + 7 x^3y^3. Hence 7 is not in the sequence.
		

References

• J. P. D'Angelo, Simon Kos and Emily Riehl. A sharp bound for the degree of proper monomial mappings between balls. J. Geom. Anal., 13(4) (2003) 581-593.

Links

• J. P. D'Angelo and J. Lebl. Complexity results for CR mappings between spheres, arXiv:0708.3232, Internat. J. Math. 20 (2) (2009) 149
• J. Lebl and D. Lichtblau, Uniqueness of certain polynomials constant on a hyperplane, arXiv:0808.0284 (2008).

Crossrefs

Cf. A143106.

Programs

Mathematica

See the paper by Lebl-Lichtblau