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 A250026 The 2-color Rado numbers for x_1^2 + x_2^2 + ... + x_n^2 = z^2. 0
 1, 7825, 105, 37, 23, 18, 20, 20, 15, 16, 20, 23, 17, 21, 26, 17, 23, 28, 25, 29, 29, 26, 36, 32, 27, 38, 33, 35, 41, 36 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The value of a(2) was only recently discovered (see Heule, Kullmann, & Marek link). - Kellen Myers, May 27 2016 REFERENCES Paul Erdős and R. L. Graham, Old and New Problems and Results in Combinatorial Number Theory, Université de Genève, L'Enseignement Mathématique 28 (1980). LINKS Table of n, a(n) for n=1..30. Marijn J. H. Heule, Oliver Kullmann, Victor W. Marek, Solving and Verifying the boolean Pythagorean Triples problem via Cube-and-Conquer arXiv:1605.00723 [math.CO], May 2016. Kellen Myers, A Note on a Question of Erdős & Graham, arXiv:1501.05085 [math.CO], Jan 2015. Kellen Myers and Joseph Parrish, Some Nonlinear Rado Numbers, Integers, 18B (2018), #A6. EXAMPLE The integers 1 through 105 cannot be 2-colored without inducing a monochromatic solution to x^2+y^2+w^2=z^2 (and 105 is the least such number), thus a(3)=105. CROSSREFS Sequence in context: A253745 A253752 A252317 * A194352 A234477 A286181 Adjacent sequences: A250023 A250024 A250025 * A250027 A250028 A250029 KEYWORD nonn,hard,more AUTHOR Kellen Myers, Nov 10 2014 EXTENSIONS a(18)-a(30) from Kellen Myers, Mar 17 2015 a(1)-a(2) from Kellen Myers, May 27 2016 STATUS approved

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Last modified May 29 03:22 EDT 2023. Contains 363029 sequences. (Running on oeis4.)