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The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet. [1]Tetrachromacy (from Greek tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye.
In graph-theoretic terms, the theorem states that for loopless planar graph, its chromatic number is ().. The intuitive statement of the four color theorem – "given any separation of a plane into contiguous regions, the regions can be colored using at most four colors so that no two adjacent regions have the same color" – needs to be interpreted appropriately to be correct.
A four-color deck (US) or four-colour pack (UK) is a deck of playing cards identical to the standard French deck except for the color of the suits. In a typical English four-color deck, hearts are red and spades are black as usual, but clubs are green and diamonds are blue. [ 2 ]
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Discharging is most well known for its central role in the proof of the four color theorem. The discharging method is used to prove that every graph in a certain class contains some subgraph from a specified list. The presence of the desired subgraph is then often used to prove a coloring result. [1]
Four color cards (Chinese: 四色牌; pinyin: Sì Sè Pái) is a game of the rummy family of card games, with a relatively long history in southern China. In Vietnam the equivalent game is known as tứ sắc ( Sino-Vietnamese pronunciation of 四色).
George David Birkhoff introduced the chromatic polynomial in 1912, defining it only for planar graphs, in an attempt to prove the four color theorem. If P ( G , k ) {\displaystyle P(G,k)} denotes the number of proper colorings of G with k colors then one could establish the four color theorem by showing P ( G , 4 ) > 0 {\displaystyle P(G,4)>0 ...
Typically, the set S has four elements (the four colours of the four colour theorem), and c is a proper colouring, that is, each pair of adjacent vertices in V are assigned distinct colours. With these additional conditions, a and b are two out of the four colours available, and every element of the ( a , b )-Kempe chain has neighbours in the ...