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A051929 Number of independent sets of vertices in graph K_4 X C_n (n > 2). 2
5, 1, 21, 73, 325, 1361, 5781, 24473, 103685, 439201, 1860501, 7881193, 33385285, 141422321, 599074581, 2537720633, 10749957125, 45537549121, 192900153621, 817138163593, 3461452808005, 14662949395601, 62113250390421, 263115950957273, 1114577054219525 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
FORMULA
a(n) = 3*a(n-1) + 5*a(n-2) + a(n-3).
From Colin Barker, May 22 2012: (Start)
a(n) = (3*(-1)^n+(2-sqrt(5))^n+(2+sqrt(5))^n).
G.f.: (5 - 14*x - 7*x^2) / ((1 + x)*(1 - 4*x - x^2)).
(End)
PROG
(PARI) Vec((5 - 14*x - 7*x^2) / ((1 + x)*(1 - 4*x - x^2)) + O(x^30)) \\ Colin Barker, May 11 2017
CROSSREFS
Row 4 of A287376.
Sequence in context: A029757 A146056 A101625 * A347487 A213118 A259682
KEYWORD
easy,nonn
AUTHOR
Stephen G Penrice, Dec 19 1999
EXTENSIONS
More terms from James A. Sellers, Dec 20 1999
STATUS
approved

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Last modified July 12 19:17 EDT 2024. Contains 374252 sequences. (Running on oeis4.)