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A084181
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2^n+(-2)^n-(-1)^n.
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1
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1, 1, 7, 1, 31, 1, 127, 1, 511, 1, 2047, 1, 8191, 1, 32767, 1, 131071, 1, 524287, 1, 2097151, 1, 8388607, 1, 33554431, 1, 134217727, 1, 536870911, 1, 2147483647, 1, 8589934591, 1, 34359738367, 1, 137438953471, 1, 549755813887, 1, 2199023255551
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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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a(n)=2^n+(-2)^n-(-1)^n;
G.f.: (1+2x+4x^2)/((1+x)(1+2x)(1-2x));
E.g.f.: exp(2x)-exp(-x)+exp(-2x).
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MATHEMATICA
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LinearRecurrence[{-1, 4, 4}, {1, 1, 7}, 50] (* or *) Riffle[ LinearRecurrence[ {5, -4}, {1, 7}, 30], 1] (* Harvey P. Dale, Jan 02 2019 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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