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 A326491 #17 Mar 04 2025 07:37:30
%S A326491 1,1,2,2,3,4,5,7,9,10,16,22,27,39,52,70,90,120,150,198,262,357,448,
%T A326491 602,782,1004,1294,1715,2229,2932,3698,4844,6259,8188,10274,13446,
%U A326491 16895,21954,27470,35843,45411,58949,73940,95200,120594,154511,192996,247967,312643
%N A326491 Number of maximal subsets of {1..n} containing no differences or quotients of pairs of distinct elements.
%F A326491 a(n) = A326497(n) + 1 for n > 1. - _Andrew Howroyd_, Aug 30 2019
%e A326491 The a(1) = 1 through a(9) = 10 subsets:
%e A326491 {1} {1} {1} {1} {1} {1} {1} {1} {1}
%e A326491 {2} {2,3} {2,3} {2,3} {2,3} {2,3,7} {2,5,6} {2,6,7}
%e A326491 {3,4} {2,5} {2,5,6} {2,5,6} {2,5,8} {3,4,5}
%e A326491 {3,4,5} {3,4,5} {2,6,7} {2,6,7} {3,5,7}
%e A326491 {4,5,6} {3,4,5} {3,4,5} {2,3,7,8}
%e A326491 {3,5,7} {3,5,7} {2,5,6,9}
%e A326491 {4,5,6,7} {2,3,7,8} {2,5,8,9}
%e A326491 {4,5,6,7} {4,5,6,7}
%e A326491 {5,6,7,8} {4,6,7,9}
%e A326491 {5,6,7,8,9}
%t A326491 fasmax[y_]:=Complement[y,Union@@(Most[Subsets[#]]&/@y)];
%t A326491 Table[Length[fasmax[Select[Subsets[Range[n]],Intersection[#,Union[Divide@@@Reverse/@Subsets[#,{2}],Subtract@@@Reverse/@Subsets[#,{2}]]]=={}&]]],{n,0,10}]
%Y A326491 Subsets without differences or quotients are A326490.
%Y A326491 Subsets with differences and quotients are A326494.
%Y A326491 Maximal subsets without differences are A121269
%Y A326491 Maximal subsets without quotients are A326492.
%Y A326491 Cf. A007865, A051026, A054519, A326023, A326117, A326489, A326496, A327591.
%K A326491 nonn
%O A326491 0,3
%A A326491 _Gus Wiseman_, Jul 09 2019
%E A326491 a(16)-a(40) from _Andrew Howroyd_, Aug 30 2019
%E A326491 a(41)-a(48) from _Jinyuan Wang_, Mar 04 2025