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 A122658 #20 May 15 2024 01:31:47
%S A122658 0,0,16,54,512,1000,3888,6174,16384,23328,50000,66550,124416,158184,
%T A122658 268912,330750,524288,628864,944784,1111158,1600000,1852200,2576816,
%U A122658 2944414,3981312,4500000,5940688,6652854,8605184,9560488,12150000,13405950,16777216,18399744
%N A122658 a(n) = if n mod 2 = 1 then n^3*(n-1)^2/2 else n^5/2.
%C A122658 Szeged index of product of two cycles of length n.
%H A122658 Janez Žerovnik, <a href="https://doi.org/10.1021/ci980148q">Szeged index of symmetric graphs</a>, J. Chem. Inf. Comput. Sci., 39 (1999), 77-80; <a href="https://scholar.archive.org/work/mjwr5vqtzjhwzlnmlpfuzsy4oq/access/wayback/http://home.postech.ac.kr:80/~arang/JCICS/1999/No.1/77.pdf">alternative link</a>.
%H A122658 <a href="/index/Rec#order_11">Index entries for linear recurrences with constant coefficients</a>, signature (1,5,-5,-10,10,10,-10,-5,5,1,-1).
%F A122658 a(n) = (n^3*(1-(-1)^n+2*(-1+(-1)^n)*n+2*n^2))/4. G.f.: 2*x^2*(x^8 +7*x^7 +95*x^6 +113*x^5 +379*x^4 +149*x^3 +189*x^2 +19*x +8) / ((x -1)^6*(x +1)^5). - _Colin Barker_, Sep 20 2013
%F A122658 Sum_{n>=2} 1/a(n) = zeta(5)/16 + 7*zeta(3)/4 + 7*zeta(2)/2 + 6*log(2) - 12. - _Amiram Eldar_, May 15 2024
%t A122658 Table[If[OddQ[n],n^3 (n-1)^2/2,n^5/2],{n,0,40}] (* or *) LinearRecurrence[ {1,5,-5,-10,10,10,-10,-5,5,1,-1},{0,0,16,54,512,1000,3888,6174,16384,23328,50000},40] (* _Harvey P. Dale_, Nov 20 2016 *)
%Y A122658 Cf. A002117, A013661, A013663, A122656.
%K A122658 nonn,easy
%O A122658 0,3
%A A122658 _N. J. A. Sloane_, Sep 22 2006