Ramsey number $R(4,4)$

The smallest number $n$ such that any two-coloring of the edges of the complete graph $K_n$ must contain either a monochromatic $K_{4}$ in the first color or a monochromatic $K_{4}$ in the second color.

Updates

• 1955 Lower bound: $18$
  R.E. Greenwood and A.M. Gleason, Combinatorial Relations and Chromatic Graphs, Canadian Journal of Mathematics, 7 (1955) 1-7.
  [via Small Ramsey Numbers, Stanisław Radziszowski, 2024-09-06]
• 1955 Upper bound: $18$
  R.E. Greenwood and A.M. Gleason, Combinatorial Relations and Chromatic Graphs, Canadian Journal of Mathematics, 7 (1955) 1-7.
  [via Small Ramsey Numbers, Stanisław Radziszowski, 2024-09-06]