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A245804
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a(n) = 2*3^n - 3*2^n.
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3
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-1, 0, 6, 30, 114, 390, 1266, 3990, 12354, 37830, 115026, 348150, 1050594, 3164070, 9516786, 28599510, 85896834, 257887110, 774054546, 2322950070, 6970423074, 20914414950, 62749536306, 188261191830, 564808741314, 1694476555590, 5083530330066, 15250792316790
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OFFSET
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0,3
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COMMENTS
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LINKS
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FORMULA
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G.f.: (-1 +5*x)/((1-2*x)(1-3*x)).
a(n) = 5*a(n-1) -6*a(n-2) for n>1.
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MATHEMATICA
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CoefficientList[Series[(-1 + 5 x)/((1 - 2 x) (1 - 3 x)), {x, 0, 30}], x]
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PROG
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(Magma) [2*3^n-3*2^n: n in [0..40]]; /* or */ I:=[-1, 0]; [n le 2 select I[n] else 5*Self(n-1)-6*Self(n-2): n in [1..30]];
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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