fourfou.rs
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$$ \definecolor{red44}{RGB}{255, 109, 107} \definecolor{green44}{RGB}{49, 207, 140} \definecolor{blue44}{RGB}{117, 184, 255} \definecolor{purple44}{RGB}{175, 112, 255} \definecolor{yellow44}{RGB}{244, 194, 13} $$
Other Four Fours Resources
"The Definitive Four Fours Answer Key"
by David A. Wheeler
" Four Fours Problem"
by Paul Bourke
The Four 4s
by Numberphile
Wikipedia Four Fours Article
Four Fours
by John Valentine