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A295168
Chromatic invariant of the 2n-crossed prism graph.
0
1, 11, 85, 521, 2869, 15017, 76717, 387425, 1945957, 9749753, 48793309, 244064849, 1220539285, 6103163369, 30516824461, 152586284993, 762936045253, 3814690056665, 19073471123773, 95367399659057, 476837091094261, 2384185650506441, 11920928661476845
OFFSET
1,2
COMMENTS
Extended to a(1) using formula/recurrence.
LINKS
Eric Weisstein's World of Mathematics, Chromatic Invariant
Eric Weisstein's World of Mathematics, Crossed Prism Graph
FORMULA
a(n) = 5^n - 2^(n - 1)*(3*n + 1).
a(n) = 9*a(n-1) - 24*a(n-2) + 20*a(n-3).
G.f. = x*(-1 - 2*x - 10*x^2)/((-1 + 2*x)^2 (-1 + 5*x)).
MATHEMATICA
Table[5^n - 2^(n - 1) (3 n + 1), {n, 20}]
LinearRecurrence[{9, -24, 20}, {1, 11, 85}, 20]
CoefficientList[Series[(-1 - 2 x - 10 x^2)/((-1 + 2 x)^2 (-1 + 5 x)), {x, 0, 20}], x]
CROSSREFS
Sequence in context: A026783 A244975 A271558 * A001240 A129180 A082365
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Nov 16 2017
STATUS
approved