login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A158411 Maximum number of colors required to paint a map having n regions. 7
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; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

The generating function can be arranged to have four zeros at the fourth roots of unity. - Jaume Oliver Lafont, Mar 23 2009

LINKS

Table of n, a(n) for n=0..100.

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. - Jaume Oliver Lafont, Mar 20 2009

G.f.: prod(k=0,3,1-I^k*x)*x/(1-x)^2. - Jaume Oliver Lafont, Mar 23 2009

a(n) = A130130(n) + A130130(n-2). - Jaume Oliver Lafont, Mar 24 2009

a(n) = min(n,4). - Wesley Ivan Hurt, Apr 16 2014

PROG

(PARI) a(n)=if(n<4, n, 4)

CROSSREFS

Cf. A000934.

Cf. A130130. - Jaume Oliver Lafont, Mar 20 2009

Sequence in context: A062750 A193669 A065686 * A065680 A093391 A210964

Adjacent sequences:  A158408 A158409 A158410 * A158412 A158413 A158414

KEYWORD

nonn,easy

AUTHOR

Jaume Oliver Lafont, Mar 18 2009

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified March 30 18:30 EDT 2017. Contains 284302 sequences.