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 A251820 #22 Jan 15 2015 13:25:42
%S A251820 15,5950
%N A251820 Numbers n for which the symmetric representation of sigma(n) has at least 3 parts, all having the same area.
%C A251820 a(3) > 36000000.
%C A251820 Also intersection of A241558 and A241559 (minimum = maximum) minus the union of A238443 and A239929 (number of parts <= 2).
%e A251820 The parts of the symmetric representations of sigma(15) and sigma(5950) are {8, 8, 8} and {4464, 4464, 4464}, respectively, so a(1) = 15 and a(2) = 5950.
%e A251820 From _Omar E. Pol_, Dec 09 2014: (Start)
%e A251820 Illustration of the symmetric representation of sigma(15) = 8 + 8 + 8 = 24 in the first quadrant:
%e A251820 .
%e A251820 . _ _ _ _ _ _ _ _ 8
%e A251820 . |_ _ _ _ _ _ _ _|
%e A251820 . |
%e A251820 . |_ _
%e A251820 . |_ |_ 8
%e A251820 . | |_
%e A251820 . |_ _ |
%e A251820 . |_|_ _ _ 8
%e A251820 . | |
%e A251820 . | |
%e A251820 . | |
%e A251820 . | |
%e A251820 . | |
%e A251820 . | |
%e A251820 . | |
%e A251820 . |_|
%e A251820 .
%e A251820 The three parts have the same area.
%e A251820 (End)
%t A251820 (* T[], row[], cD[] & tD[] are defined in A239663 *)
%t A251820 a251820[n_] := Module[{pT = T[n, 1], cT, cL, cW = 0, cR = 0, sects = {}, j = 1, r = row[n], test = True}, While[test && j <= r, cT = T[n, j+1]; cL = pT - cT; cW += (-1)^(j+1) * tD[n, j]; If[cW == 0 && cR != 0, AppendTo[sects, cR]; cR = 0; If[Min[sects] != Max[sects], test = False], cR += cL * cW]; pT = cT; j++]; If[cW != 0, AppendTo[sects, 2 * cR - cW]]; Min[sects] == Max[sects] && Length[sects] > 1]
%t A251820 Select[Range[50000], a251820] (* data *)
%Y A251820 Cf. A000203, A237593, A237270, A238443, A239663, A241558, A241559.
%K A251820 nonn,more,hard,bref
%O A251820 1,1
%A A251820 _Hartmut F. W. Hoft_, Dec 09 2014