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 A365195 #59 Oct 22 2023 22:58:47 %S A365195 1,2,2,4,3,6,4,8,5,9,6,12,7,12,8,16,9,18,10,20,11,18,12,24,13,21,14, %T A365195 28,15,30,16,32,17,27,18,36,19,30,20,40,21,42,22,42,23,36,24,48,25,39, %U A365195 26,49,27,54,28,56,29,45,30,60,31,48,32,64,33,66,34,63,35,54,36,72,37,57,38,70,39,77,40,80 %N A365195 Height of the first staircase of the ziggurat of order n described in A347186. %C A365195 a(n) is also the number of square cells in the first layer of the symmetric representation of sigma(n) from the border to, at most, the axis of symmetry of the diagram. %C A365195 The values of a(n) where a(n) = n give A174973. %C A365195 Since this is a supersequence of A174973 so all powers of 2 and all even perfect numbers are in the sequence. %C A365195 From _Omar E. Pol_, Oct 22 2023: (Start) %C A365195 The values of a(n) where a(n) is not equal to n give A238524. %C A365195 If n is an odd prime then a(n) = (n + 1)/2. %C A365195 Shares infinitely many terms with A365433 from which first differs at a(15). (End) %F A365195 a(n) <= n. %F A365195 a(2*n-1) = n. %Y A365195 Cf. A000079, A000396, A065091, A174973, A196020, A235791, A236104, A237270, A237271, A237591, A237593, A238524, A262626, A279387, A347186, A347367, A365433, A365434. %K A365195 nonn %O A365195 1,2 %A A365195 _Omar E. Pol_, Aug 25 2023 %E A365195 More terms from _Omar E. Pol_, Oct 22 2023