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%I #20 Jun 13 2015 00:55:36
%S 1,4,11,36,119,408,1419,4988,17631,62528,222163,790180,2812135,
%T 10011304,35647259,126942540,452078447,1610033040,5734081251,
%U 20421960308,72733344375,259042555640,922591559467,3285854197276,11702734525951,41679889602784,148445093121011,528694969090116
%N a(0)=1, a(1)=4; thereafter a(n) = a(n-2)+2*A055099(n-1)+2^(n-1).
%H Colin Barker, <a href="/A256960/b256960.txt">Table of n, a(n) for n = 0..1000</a>
%H J. Goldwasser et al., <a href="http://dx.doi.org/10.1016/S0012-365X(98)00373-2">The density of ones in Pascal's rhombus</a>, Discrete Math., 204 (1999), 231-236.
%H Paul K. Stockmeyer, <a href="http://arxiv.org/abs/1504.04404">The Pascal Rhombus and the Stealth Configuration</a>, arXiv:1504.04404 [math.CO], 2015.
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,1,-8,-4).
%F G.f.: -(2*x+1)*(2*x^2+2*x-1) / ((x+1)*(2*x-1)*(2*x^2+3*x-1)). - _Colin Barker_, Jun 05 2015
%o (PARI) Vec(-(2*x+1)*(2*x^2+2*x-1)/((x+1)*(2*x-1)*(2*x^2+3*x-1)) + O(x^100)) \\ _Colin Barker_, Jun 06 2015
%Y Cf. A055099.
%K nonn,easy
%O 0,2
%A _N. J. A. Sloane_, Apr 14 2015