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A101604
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a(n) = 2*a(n-1) + 5*a(n-2) + 2*a(n-3).
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0
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1, 2, 9, 30, 109, 386, 1377, 4902, 17461, 62186, 221481, 788814, 2809405, 10005842, 35636337, 126920694, 452034757, 1609945658, 5733906489, 20421610782, 72732645325, 259041157538, 922588763265, 3285848604870, 11702723341141
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OFFSET
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0,2
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COMMENTS
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Transform of 2^n under Riordan array A101603.
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LINKS
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FORMULA
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G.f.: 1/((1+x)*(1-3*x-2*x^2));
a(n) = (3/4 + sqrt(17)/4)^n*(1/4 + 7*sqrt(17)/68) + (1/4 - 7*sqrt(17)/68)*(3/4 - sqrt(17)/4)^n + (-1)^n/2;
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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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