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A273399
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a(n) = Catalan(Catalan(n)).
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1
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OFFSET
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0,3
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COMMENTS
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Next term, a(7), which has 255 digits and is equal to Catalan(429), is too large to include.
The number of digits of a(n) grows faster than Fibonacci(n) or Catalan(n-1), but slower than Catalan(n).
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LINKS
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FORMULA
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EXAMPLE
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a(3) = Catalan(Catalan(3)) = Catalan(5) = 42.
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MAPLE
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a:= ((n-> binomial(2*n, n)/(n+1))@@2):
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MATHEMATICA
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CatalanNumber[CatalanNumber[Range[0, 6]]]
Table[CatalanNumber[CatalanNumber[n]], {n, 0, 6}]
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PROG
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for(n=0, 6, cn=binomial(2*n, n)/(n+1); cn2=binomial(2*cn, cn)/(cn+1); print1(cn2 ", "))
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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