A158515 Number of colors needed to paint a wheel graph on n nodes.

0, 1, 2, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4

Offset: 0

Author

Jaume Oliver Lafont, Mar 20 2009

Keywords

• nonn
• easy

Comments

Adjacent nodes are not allowed to have the same color.

Links

• Antti Karttunen, Table of n, a(n) for n = 0..1001
• Eric Weisstein's World of Mathematics, Wheel Graph
• Wikipedia, Wheel graph
• Index entries for linear recurrences with constant coefficients, signature (0,1).

Crossrefs

Cf. A158411, A158478.

Programs

Mathematica

PadRight[{0, 1, 2}, 100, {4, 3}] (* Paolo Xausa, Apr 22 2024 *)

PARI

a(n)=if(n<4,n,4-n%2)

Scheme

(define (A158515 n) (if (< n 4) n (- 4 (modulo n 2)))) ;; Antti Karttunen, Sep 14 2017

Formula

G.f.: x*(1+2*x+2*x^2+2*x^3)/(1-x^2)