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A326172
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Number of nonempty subsets of {2..n} whose product is divisible by their sum.
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2
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0, 0, 1, 2, 3, 6, 12, 21, 34, 69, 140, 278, 561, 1144, 2367, 4936, 9503, 19368, 38202, 77911, 156458, 318911, 651462, 1329624, 2596458, 5144833, 10494839, 20500025, 40923643, 83620258, 164982516, 335873558, 651383048, 1310551707, 2655240565, 5295397093, 10338145110, 21052407259, 42748787713, 86078893923, 169349494068
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OFFSET
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0,4
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LINKS
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Table of n, a(n) for n=0..40.
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EXAMPLE
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The a(2) = 1 through a(7) = 21 subsets:
{2} {2} {2} {2} {2} {2}
{3} {3} {3} {3} {3}
{4} {4} {4} {4}
{5} {5} {5}
{2,3,5} {6} {6}
{3,4,5} {3,6} {7}
{2,3,5} {3,6}
{2,4,6} {2,3,5}
{3,4,5} {2,4,6}
{4,5,6} {2,5,7}
{3,4,5,6} {3,4,5}
{2,3,4,5,6} {3,4,7}
{3,5,7}
{4,5,6}
{2,3,6,7}
{2,5,6,7}
{3,4,5,6}
{3,5,6,7}
{2,3,4,5,6}
{2,3,4,5,7}
{2,4,5,6,7}
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MATHEMATICA
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Table[Length[Select[Subsets[Range[2, n], {1, n}], Divisible[Times@@#, Plus@@#]&]], {n, 0, 10}]
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CROSSREFS
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Cf. A053632, A057567, A057568, A059529, A063865, A301987, A325037, A325044, A326150, A326151, A326153/A326154, A326155, A326156, A326158, A326178.
Sequence in context: A096571 A227940 A081156 * A082877 A047090 A185265
Adjacent sequences: A326169 A326170 A326171 * A326173 A326174 A326175
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KEYWORD
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nonn
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AUTHOR
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Gus Wiseman, Jun 11 2019
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EXTENSIONS
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a(21)-a(29) from Alois P. Heinz, Jun 13 2019
a(30)-a(40) from Bert Dobbelaere, Jun 22 2019
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STATUS
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approved
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