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Number of 4-element nondividing subsets of {1, 2, ..., n}.
1

%I #9 Mar 09 2018 12:20:24

%S 1,2,3,6,10,21,32,49,65,101,150,224,305,413,525,707,908,1174,1479,

%T 1871,2269,2826,3396,4138,4967,5991,6917,8244,9673,11328,12958,15091,

%U 17112,19771,22468,25485,28870,32861,36298,40969,45615,51015

%N Number of 4-element nondividing subsets of {1, 2, ..., n}.

%C A set is called nondividing if no element divides the sum of any nonempty subset of the other elements.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/NondividingSet.html">Nondividing Set</a>

%e a(10) = 1 because there is one 4-element nondividing subset of {1,2,...,10}: {6,7,9,10}.

%Y Column 4 of triangle A187489. Cf. A068063.

%K nonn

%O 10,2

%A _Alois P. Heinz_, Mar 10 2011