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 A319850 #5 Sep 30 2018 20:26:56
%S A319850 1,2,5,21,94,446,2287,12568,78509
%N A319850 Number of distinct positive integers that can be obtained, starting with the initial interval partition (1, ..., n), by iteratively adding or multiplying together parts until only one part remains.
%e A319850 The n-th row lists all integers that can be obtained starting with (1, ..., n):
%e A319850 1
%e A319850 2 3
%e A319850 5 6 7 8 9
%e A319850 9 10 11 12 13 14 15 16 17 18 19 20 21 24 25 26 27 28 30 32 36
%t A319850 ReplaceListRepeated[forms_,rerules_]:=Union[Flatten[FixedPointList[Function[pre,Union[Flatten[ReplaceList[#,rerules]&/@pre,1]]],forms],1]];
%t A319850 Table[Length[Select[ReplaceListRepeated[{Range[n]},{{foe___,x_,mie___,y_,afe___}:>Sort[Append[{foe,mie,afe},x+y]],{foe___,x_,mie___,y_,afe___}:>Sort[Append[{foe,mie,afe},x*y]]}],Length[#]==1&]],{n,6}]
%Y A319850 Cf. A000041, A001055, A001970, A048249, A066739, A066815, A070960, A201163, A318948, A318949, A319841.
%K A319850 nonn,more
%O A319850 1,2
%A A319850 _Gus Wiseman_, Sep 29 2018