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%I #8 Aug 14 2013 13:59:55
%S 1,1,2,0,9,54,459,2568,20145,176076,1833741,20148336,241870617,
%T 3132196560,43874128089,658195206264,10533823597089,179062417518768,
%U 3223079582143185,61237777946016096,1224762717659002281,25720036368344942616,565841009719801635777
%N Number of permutations of n objects such that no three-element subset is preserved.
%C The limit as n -> infinity of a(n)/n! = (3+2*exp(1/2))/(2*exp(11/6)) or approximately 0.5034167572.
%F E.g.f.:((x+x^2/2)*exp(-x-x^2/2-x^3/3)+exp(-x-x^3/3))/(1-x)
%e Example: For n=5 the only permutations that fix no three-element subset are the 24 5-cycles and the 30 4-cycles, therefore a(5)=54.
%o (PARI) lista(nn) = {x=xx+O(xx^nn); egf=((x+x^2/2)*exp(-x-x^2/2-x^3/3)+exp(-x-x^3/3))/(1-x); Vec(serlaplace(egf)) ;} \\ _Michel Marcus_, Aug 14 2013
%Y Cf. A000166, A137482, A213323, A213324.
%K nonn
%O 0,3
%A _Les Reid_, Jun 08 2012
%E More terms from _Michel Marcus_, Aug 14 2013
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