id:A158411 - OEIS Search Results

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Maximum number of colors required to paint a map having n regions.

+0
6

0, 1, 2, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4 (list; graph; listen)

	OFFSET	`0,3`
	COMMENT	`The generating function can be arranged to have four zeros at the fourth roots of unity. [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Mar 23 2009]`
	LINKS	`Wikipedia, Four color theorem` `Wolfram Mathworld, Four-Color Theorem`
	FORMULA	`G.f.: x(1+x+x^2+x^3)/(1-x)` `G.f.: x(1-x^4)/(1-x)^2 [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Mar 20 2009]` `G.f.: prod(k=0,3,1-I^kx)x/(1-x)^2 [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Mar 23 2009]`
	PROGRAM	`(PARI) a(n)=if(n<4, n, 4)`
	CROSSREFS	`Cf. A000934.` `Cf. A130130. [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Mar 20 2009]` `a(n)=A130130(n)+A130130(n-2) [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Mar 24 2009]` `Sequence in context: A030241 A062750 A065686 this_sequence A065680 A093391 A029135` `Adjacent sequences: A158408 A158409 A158410 this_sequence A158412 A158413 A158414`
	KEYWORD	`nonn`
	AUTHOR	`Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Mar 18 2009`

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Last modified November 27 14:50 EST 2009. Contains 167570 sequences.

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