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A133927
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Numbers k such that the sum of the first k Catalan numbers, C_1 + C_2 + ... + C_k, is divisible by k.
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0
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OFFSET
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1,2
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COMMENTS
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The sum of the first 30 Catalan numbers, 1 + 2 + 5 + ... + 3814986502092304 = 5175497420902740, is divisible by 30, so 30 is a term.
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LINKS
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MATHEMATICA
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Module[{nn=40000, lst}, lst=Thread[{Range[nn], Accumulate[CatalanNumber[Range[nn]]]}]; Position[ lst, _?(Mod[#[[2]], #[[1]]]==0&), 1, Heads->False]]//Flatten (* The program generates the first 5 terms of the sequence. *) (* Harvey P. Dale, Jun 18 2024 *)
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CROSSREFS
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KEYWORD
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hard,more,nonn
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AUTHOR
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STATUS
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approved
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