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Search: id:A107756
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| A107756 |
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Numbers n such that Sum_{k=1..n} Catalan(k) == 1 mod 3. |
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+0
4
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| 1, 4, 5, 6, 7, 10, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 28, 31, 32, 33, 34, 37, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 82, 85, 86, 87, 88, 91, 94, 95
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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Y. More, Problem 11165, Amer. Math. Monthly, 112 (2005), 568.
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FORMULA
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Equivalently, numbers n such that base 3 expansion of n+1 contains a 2.
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MATHEMATICA
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Select[ Range[ 100], Mod[ Sum[(2 n)!/n!/(n + 1)!, {n, #}], 3] == 1 &] (from Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 14 2005)
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CROSSREFS
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Cf. A000108, A107755, A107757.
Equals A074940 - 1.
Sequence in context: A123438 A039024 A065028 this_sequence A080723 A022561 A047312
Adjacent sequences: A107753 A107754 A107755 this_sequence A107757 A107758 A107759
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Jun 11 2005
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