login
a(n) = (n+1)(n+2)^2*(n+3)^2*(n+4)(11n^4 + 110n^3 + 439n^2 + 820n + 600)/86400.
2

%I #12 Jun 13 2015 00:51:50

%S 1,33,421,3171,16954,71148,249228,758934,2066559,5135845,11828817,

%T 25546885,52216164,101751664,190171248,342572508,597234429,1011161361,

%U 1667449861,2684929863,4230610846,6535551660,9914869900,14792713650,21733135515,31477936581

%N a(n) = (n+1)(n+2)^2*(n+3)^2*(n+4)(11n^4 + 110n^3 + 439n^2 + 820n + 600)/86400.

%C Kekulé numbers for certain benzenoids.

%D S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 229).

%H T. D. Noe, <a href="/A107965/b107965.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_11">Index entries for linear recurrences with constant coefficients</a>, signature (11,-55,165,-330,462,-462,330,-165,55,-11,1).

%F G.f.: -(x^6+22*x^5+113*x^4+190*x^3+113*x^2+22*x+1) / (x-1)^11. - _Colin Barker_, Aug 13 2013

%p a:=n->(1/86400)*(n+1)*(n+2)^2*(n+3)^2*(n+4)*(11*n^4+110*n^3+439*n^2+820*n+600): seq(a(n),n=0..26);

%K nonn,easy

%O 0,2

%A _Emeric Deutsch_, Jun 12 2005