login
A332348
Number of maximal independent sets in the 3 X n king graph.
2
1, 2, 6, 8, 22, 40, 82, 176, 340, 722, 1450, 2966, 6096, 12362, 25384, 51728, 105698, 216074, 440962, 901396, 1840686, 3760232, 7681828, 15689962, 32053346, 65473214, 133745304, 273208346, 558081744, 1140024080, 2328745042, 4757002434, 9717279194, 19849727740
OFFSET
0,2
FORMULA
a(n) = a(n-1) + 2*a(n-2) + a(n-3) - 2*a(n-4) + 2*a(n-5) - 2*a(n-6) for n >= 6.
G.f.: (1 + x + 2*x^2 - 3*x^3 + 2*x^4 - 2*x^5)/(1 - x - 2*x^2 - x^3 + 2*x^4 - 2*x^5 + 2*x^6).
PROG
(PARI) Vec((1 + x + 2*x^2 - 3*x^3 + 2*x^4 - 2*x^5)/(1 - x - 2*x^2 - x^3 + 2*x^4 - 2*x^5 + 2*x^6) + O(x^40))
CROSSREFS
Row n=3 of A332347.
Sequence in context: A129342 A045654 A081672 * A137072 A153802 A217019
KEYWORD
nonn,easy
AUTHOR
Andrew Howroyd, Feb 10 2020
STATUS
approved