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%I #18 Jun 13 2015 00:51:54
%S 0,0,0,3,5,7,18,22,26,45,51,57,84,92,100,135,145,155,198,210,222,273,
%T 287,301,360,376,392,459,477,495,570,590,610,693,715,737,828,852,876,
%U 975,1001,1027,1134,1162,1190,1305,1335,1365,1488,1520,1552,1683,1717,1751,1890
%N Crossing number of K_{4,n} on the real projective plane.
%H P. T. Ho, <a href="http://dx.doi.org/10.1016/j.disc.2005.09.010">The crossing number of K_{4,n} on the real projective plane</a>, Discr. Math., 304 (2005), pp. 23-33.
%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,2,-2,0,-1,1).
%F a(n) = floor(n/3)*(2*n-3(1+floor(n/3))).
%F G.f.: -x^3*(5*x^3+2*x^2+2*x+3) / ((x-1)^3*(x^2+x+1)^2). - _Colin Barker_, Mar 06 2014
%Y Cf. A008724.
%K nonn,easy
%O 0,4
%A _N. J. A. Sloane_, Dec 24 2005
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