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%I #6 Jul 26 2013 15:54:28
%S 0,0,0,2,3,4,8,11,15,26,35,47,80,107,143,242,323,431,728,971,1295,
%T 2186,2915,3887,6560,8747,11663,19682,26243,34991,59048,78731,104975,
%U 177146,236195,314927,531440,708587,944783,1594322,2125763,2834351,4782968,6377291,8503055,14348906
%N Clique number of commuting graph of alternating group A_n.
%C The graph is empty for n = 0, 1 and 2, so a(n) = 0 by convention (or should it be 1?).
%D A. Iranmanesh and A. Jafarzadeh, On the commuting graph associated with the symmetric and alternating groups, J. Algebra and Applic., 7 (2008), 129-146.
%F Conjecture: a(n) = a(n-1)+3*a(n-3)-3*a(n-4) for n>6. G.f.: -x^3*(x^6-x^5+2*x^3-x^2-x-2) / ((x-1)*(3*x^3-1)). - _Colin Barker_, Jul 26 2013
%K nonn
%O 0,4
%A _N. J. A. Sloane_, Mar 07 2008