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%I #16 Mar 17 2023 02:03:45
%S 1,2,5,12,29,68,158,360,813,1812,4010,8792,19170,41512,89500,191952,
%T 410237,873140,1853042,3919608,8271126,17406072,36556580,76602032,
%U 160240594,334554248,697462628,1451633520,3017426468,6263171792,12985655736,26889935776,55626815005,114947516916,237318165314,489482593592,1008787357902,2077219057240,4274204436052
%N Expansion of g.f. (3-4*x-sqrt(1-4*x^2))/(2*(1-2*x)^2).
%H F. Disanto and S. Rinaldi, <a href="http://www.mat.unisi.it/newsito/puma/public_html/22_1/2-disanto_rinaldi.pdf">Symmetric convex permutominoes and involutions</a>, PU. M. A., Vol. 22 (2011), No. 1, pp. 39-60; See M_n.
%F G.f.: (3-4*x-sqrt(1-4*x^2))/(2*(1-2*x)^2).
%F D-finite with recurrence: n*(n-4)*a(n) +2*(5+2n-n^2)*a(n-1) -4*(n-2)*(n-5)*a(n-2) +8*(n-2)*(n-3)*a(n-3)=0. - _R. J. Mathar_, Jun 28 2012
%F a(n) ~ n*2^(n-1) * (1-2*sqrt(2/Pi)/sqrt(n)). - _Vaclav Kotesovec_, Jun 29 2013
%K nonn
%O 0,2
%A _N. J. A. Sloane_, May 05 2012
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