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 A326023 #10 Aug 30 2019 21:47:16 %S A326023 1,2,3,5,9,17,25,49,73,145,217,433,553,1105,1657,2593,3937,7873,10057, %T A326023 20113,26689,42321,63481,126961,154801,309601,464401,737569,992161, %U A326023 1984321,2450881,4901761,6292801,10197313,15295969,26241697,32947489,65894977,98842465,161587873,205842529 %N A326023 Number of subsets of {1..n} containing all of their integer quotients. %C A326023 These are sets that are closed under taking the quotient of two (not necessarily distinct) divisible terms. %F A326023 For n > 0, a(n) = A326078(n) + 1. %e A326023 The a(0) = 1 through a(5) = 17 subsets: %e A326023 {} {} {} {} {} {} %e A326023 {1} {1} {1} {1} {1} %e A326023 {1,2} {1,2} {1,2} {1,2} %e A326023 {1,3} {1,3} {1,3} %e A326023 {1,2,3} {1,4} {1,4} %e A326023 {1,2,3} {1,5} %e A326023 {1,2,4} {1,2,3} %e A326023 {1,3,4} {1,2,4} %e A326023 {1,2,3,4} {1,2,5} %e A326023 {1,3,4} %e A326023 {1,3,5} %e A326023 {1,4,5} %e A326023 {1,2,3,4} %e A326023 {1,2,3,5} %e A326023 {1,2,4,5} %e A326023 {1,3,4,5} %e A326023 {1,2,3,4,5} %t A326023 Table[Length[Select[Subsets[Range[n]],SubsetQ[#,Select[Divide@@@Tuples[#,2],IntegerQ]]&]],{n,0,10}] %Y A326023 Cf. A007865, A051026, A054519, A067992, A103580, A325853, A325854, A325860, A325861, A325994, A326078. %K A326023 nonn %O A326023 0,2 %A A326023 _Gus Wiseman_, Jun 04 2019 %E A326023 Terms a(21) and beyond from _Andrew Howroyd_, Aug 30 2019