This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A187492 #10 Feb 16 2025 08:33:14
%S A187492 2,4,6,11,15,24,50,83,127,209,310,431,679,921,1229,1624,2145,2770,
%T A187492 3752,4866,6141,7753,9679,12005,15027,18134,22045,26368,31712,37763,
%U A187492 45569,53810,63393,73560,86496,100071,117234,134623,155465,176876
%N A187492 Number of 5-element nondividing subsets of {1, 2, ..., n}.
%C A187492 A set is called nondividing if no element divides the sum of any nonempty subset of the other elements.
%H A187492 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/NondividingSet.html">Nondividing Set</a>
%e A187492 a(21) = 2 because there are two 5-element nondividing subsets of {1,2,...,21}: {12,16,18,19,21}, {12,14,18,20,21}.
%Y A187492 Column 5 of triangle A187489. Cf. A068063.
%K A187492 nonn
%O A187492 21,1
%A A187492 _Alois P. Heinz_, Mar 10 2011