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A006342 Coloring a circuit with 4 colors.
(Formerly M3398)
+0
2
1, 1, 4, 10, 31, 91, 274, 820, 2461, 7381, 22144, 66430, 199291, 597871, 1793614, 5380840, 16142521, 48427561, 145282684, 435848050, 1307544151, 3922632451, 11767897354, 35303692060, 105911076181, 317733228541 (list; graph; listen)
OFFSET

0,3

REFERENCES

S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures}, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.

F. R. Bernhart, Topics in Graph Theory Related to the Five Color Conjecture. Ph.D. Dissertation, Kansas State Univ., 1974.

G. D. Birkhoff, D. C. Lewis, Chromatic polynomials. Trans. Amer. Math. Soc. 60, (1946). 355-451.

LINKS

S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures}, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.

S. Plouffe, 1031 Generating Functions and Conjectures, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.

FORMULA

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

Binomial transform of A002001 (with interpolated zeros). Partial sums of A054878. E.g.f.: exp(x)(3cosh(2x)+1)/4; a(n)=3*3^n/8+1/4+3(-1)^n/8=sum{k=0..n, (3^k+3(-1)^k)/4 }. - Paul Barry (pbarry(AT)wit.ie), Sep 03 2003

MAPLE

A006342:=-(-1+2*z)/(z-1)/(3*z-1)/(z+1); [Conjectured by S. Plouffe in his 1992 dissertation.]

a[0]:=0:a[1]:=1:for n from 2 to 50 do a[n]:=2*a[n-1]+3*a[n-2]-1 od: seq(a[n], n=1..26); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 28 2008

CROSSREFS

Sequence in context: A067142 A034730 A095127 this_sequence A135831 A015796 A034717

Adjacent sequences: A006339 A006340 A006341 this_sequence A006343 A006344 A006345

KEYWORD

nonn

AUTHOR

njas, Simon Plouffe (plouffe(AT)math.uqam.ca)

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Last modified July 23 17:35 EDT 2008. Contains 142285 sequences.


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