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 A123351 #11 Jul 26 2019 04:32:44
%S A123351 1,4,30,146,517,1476,3614,7890,15761,29332,51526,86274,138725,215476,
%T A123351 324822,477026,684609,962660,1329166,1805362,2416101,3190244,4161070,
%U A123351 5366706,6850577,8661876,10856054,13495330,16649221,20395092,24818726
%N A123351 Kekulé numbers for certain benzenoids (see the Cyvin-Gutman book for details).
%H A123351 S. J. Cyvin and I. Gutman, <a href="https://doi.org/10.1007/978-3-662-00892-8_8">Kekulé structures in benzenoid hydrocarbons</a>, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (see p. 120 and K{Ch(m,3)} page 119).
%F A123351 G.f.: -x*(2*x^6-8*x^5+20*x^4-15*x^3+23*x^2-3*x+1) / (x-1)^7. - _Colin Barker_, Aug 29 2013
%p A123351 A123351 := proc(n)
%p A123351 (n^6+6*n^5+22*n^4+30*n^3+49*n^2+36)/36 ;
%p A123351 end proc:
%p A123351 seq( A123351(n),n=0..30) ; # _R. J. Mathar_, Jul 26 2019
%K A123351 nonn,easy
%O A123351 0,2
%A A123351 _N. J. A. Sloane_, Oct 10 2006