OFFSET
1,1
COMMENTS
a(n) is the minimal degree of an equation from which n successive terms after the first can be removed (by a series of transformation comparable to Tschirnhaus's) without requiring the solution of at least one irreducible equation of degree greater than n. The cases where an equation of degree greater than n is needed but is in fact factorizable into several equations of degree all less than or equal to n are considered as fair. a(n) <= A000905(n) by definition.
REFERENCES
W. R. Hamilton, Sixth Report of the British Association for the Advancement of Science, London, 1831, 295-348.
LINKS
Raymond Garver, The Tschirnhaus transformation, The Annals of Mathematics, 2nd Ser., Vol. 29, No. 1/4. (1927 - 1928), pp. 330.
E. Lucas, Théorie des Nombres, Gauthier-Villars, Paris, 1891, Vol. 1, p. 496.
J. J. Sylvester and M. J. Hammond, On Hamilton's numbers, Phil. Trans. Roy. Soc., 178 (1887), 285-312.
EXAMPLE
a(4)=10 because one can remove 4 terms in an equation of degree 10 by solving two quartic equations.
CROSSREFS
KEYWORD
more,nice,nonn
AUTHOR
Olivier Gérard, Oct 17 2007
STATUS
approved