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A309185
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(1/6) times the number of n-member subsets of [6n] whose elements sum to a multiple of n.
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2
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1, 5, 46, 445, 4751, 54086, 642342, 7861661, 98480332, 1256564755, 16273981758, 213378975958, 2826867619109, 37782552518478, 508840821830546, 6898459216311581, 94070535317459018, 1289430373107971804, 17755914760643605782, 245518560760433579195
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OFFSET
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1,2
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COMMENTS
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Also (1/5) times the number of n-member subsets of [6n-1] whose elements sum to a multiple of n.
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LINKS
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FORMULA
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a(n) = 1/(6n) * Sum_{d|n} binomial(6d,d)*(-1)^(n+d)*phi(n/d).
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MAPLE
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with(numtheory):
a:= n-> add(binomial(6*d, d)*(-1)^(n+d)*
phi(n/d), d in divisors(n))/(6*n):
seq(a(n), n=1..25);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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