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%I #5 May 28 2017 09:31:50
%S 1,2,4,9,20,45,100,222,491,1086,2401,5310,11744,25977,57460,127101,
%T 281144,621882,1375579,3042726,6730385,14887338,32930188,72840249,
%U 161119700,356390301,788321020,1743734406,3857070395,8531684622
%N Number of (3412,2341)-, (3412,4123)- and (3412,52341)-avoiding involutions in S_n.
%H E. S. Egge, <a href="http://arXiv.org/abs/math.CO/0307050">Restricted 3412-Avoiding Involutions: Continued Fractions, Chebyshev Polynomials and Enumerations</a>, sec. 8
%F G.f. (1-x^2)*(1-x)^2/(1-3*x+x^2+3*x^3-3*x^4).
%t CoefficientList[Series[(1-x^2)(1-x)^2/(1-3x+x^2+3x^3-3x^4),{x,0,40}],x] (* _Harvey P. Dale_, May 28 2017 *)
%K nonn,easy
%O 1,2
%A _Ralf Stephan_, Jul 06 2003
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