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A368956
a(n) = 3^n - 2^(n+1) - 1.
1
-2, 0, 10, 48, 178, 600, 1930, 6048, 18658, 57000, 173050, 523248, 1577938, 4750200, 14283370, 42915648, 128878018, 386896200, 1161212890, 3484687248, 10456158898, 31372671000, 94126401610, 282395982048, 847221500578, 2541731610600, 7625329049530
OFFSET
1,1
COMMENTS
For even n >= 4, also the number of minimum vertex colorings of the n-Moebius ladder.
LINKS
Eric Weisstein's World of Mathematics, Minimum Vertex Coloring.
Eric Weisstein's World of Mathematics, Moebius Ladder.
FORMULA
a(n) = 6*(n-1) - 11*a(n-2) + 6*a(n-3).
G.f.: 2*x*(1-6*x+6*x^2)/((-1+x)*(-1+2*x)*(-1+3*x)).
MATHEMATICA
Table[3^n - 2^(n + 1) - 1, {n, 20}]
LinearRecurrence[{6, -11, 6}, {-2, 0, 10}, 20]
CoefficientList[Series[2 (1 - 6 x + 6 x^2)/((-1 + x) (-1 + 2 x) (-1 + 3 x)), {x, 0, 20}], x]
PROG
(Python)
def A368956(n): return 3**n-(1<<n+1)-1 # Chai Wah Wu, Mar 05 2024
CROSSREFS
Sequence in context: A065624 A086890 A167387 * A035237 A189423 A342287
KEYWORD
sign,easy
AUTHOR
Eric W. Weisstein, Mar 05 2024
STATUS
approved