cp's OEIS Frontend

A212751 Number of (w,x,y,z) with all terms in {0,...,n} and at least one of these conditions holds: w=R, x=R, y=R, z where R = max{w,x,y,z} - min{w,x,y,z}.

%I A212751 #13 Jun 13 2015 00:54:14
%S A212751 1,14,70,198,477,924,1696,2768,4405,6510,9486,13134,18025,23828,31312,
%T A212751 39984,50841,63198,78310,95270,115621,138204,164880,194208,228397,
%U A212751 265694,308686,355278,408465,465780,530656,600224,678385,761838
%N A212751 Number of (w,x,y,z) with all terms in {0,...,n} and at least one of these conditions holds: w=R, x=R, y=R, z<R, where R = max{w,x,y,z} - min{w,x,y,z}.
%C A212751 For a guide to related sequences, see A211795.
%H A212751 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (2,2,-6,0,6,-2,-2,1)
%F A212751 a(n)=2*a(n-1)+2*a(n-2)-6*a(n-3)+6*a(n-5)-2*a(n-6)-2*a(n-7)+a(n-8).
%F A212751 G.f.: ( -1-12*x-40*x^2-36*x^3-25*x^4+12*x^5 ) / ( (1+x)^3*(x-1)^5 ).
%t A212751 t = Compile[{{n, _Integer}},
%t A212751 Module[{s = 0}, (Do[
%t A212751 If[(w == # || x == # || y == # || z < #) &[
%t A212751 Max[w, x, y, z] - Min[w, x, y, z]], s++], {w, 0, n}, {x, 0, n}, {y, 0, n}, {z, 0, n}]; s)]];
%t A212751 Map[t[#] &, Range[0, 40]] (* A212751 *)
%t A212751 (* _Peter J. C. Moses_, May 24 2012 *)
%Y A212751 Cf. A211795.
%K A212751 nonn,easy
%O A212751 0,2
%A A212751 _Clark Kimberling_, May 27 2012