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A063017
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a(n) = Catalan(n)*(3^(n+1) - 2^(n+1) + 1)/2.
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2
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1, 3, 20, 165, 1484, 13986, 135960, 1352637, 13707980, 141061206, 1470489800, 15500280978, 164967244792, 1770548369700, 19143828730800, 208347968093085, 2280730450967820, 25096531231958670, 277445318198433000
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = Catalan(n)*(3^(n+1) - 2^(n+1) + 1)/2;
o.g.f: -(sqrt(1-4x) - sqrt(1-8x)+ sqrt(1-12x) -1)/(4x).
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MATHEMATICA
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Table[CatalanNumber[n] (3^(n + 1) - 2^(n + 1) + 1)/2, {n, 0, 20}] (* Wesley Ivan Hurt, Jan 30 2014 *)
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PROG
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(PARI) a(n)={binomial(2*n, n)/(n + 1)*(3^(n+1) - 2^(n+1) + 1)/2} \\ Harry J. Smith, Aug 16 2009
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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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EXTENSIONS
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STATUS
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approved
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