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 A078876 #25 May 31 2022 03:37:50
%S A078876 0,0,1,27,272,1625,6993,24010,69888,179334,416625,893101,1791504,
%T A078876 3398759,6148961,10678500,17895424,29065308,45916065,70764303,
%U A078876 106666000,157594437,228648497,326294606,458645760,635781250,870110865,1176787521,1574172432,2084357107
%N A078876 a(n) = n^4*(n^4-1)/240.
%C A078876 Kekulé numbers for certain benzenoids. - _Emeric Deutsch_, Jun 12 2005
%C A078876 For n>=2, the triple (n^6, 120*a(n), (n^8 + n^4)/2) form a Pythagorean triple whose short leg is a square and the other sides are triangular numbers. - _Michel Marcus_, Mar 15 2021
%D A078876 S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 230, #14).
%H A078876 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (9,-36,84,-126,126,-84,36,-9,1).
%F A078876 G.f.: -x^2*(x+1)*(x^4+17*x^3+48*x^2+17*x+1) / (x-1)^9. - _Colin Barker_, Jun 18 2013
%F A078876 From _Amiram Eldar_, May 31 2022: (Start)
%F A078876 Sum_{n>=2} 1/a(n) = 450 - 8*Pi^4/3 - 60*Pi*coth(Pi).
%F A078876 Sum_{n>=2} (-1)^n/a(n) = 7*Pi^4/3 - 60*Pi*cosech(Pi) - 210. (End)
%t A078876 Table[n^4*(n^4 - 1)/240, {n, 0, 30}] (* _Amiram Eldar_, May 31 2022 *)
%Y A078876 Cf. A002415.
%Y A078876 Cf. A001014 (n^6), A071231 ((n^8 + n^4)/2).
%K A078876 nonn,easy
%O A078876 0,4
%A A078876 _Benoit Cloitre_, Jan 11 2003