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%I #20 Feb 19 2018 03:37:39
%S 1,19,78,202,415,741,1204,1828,2637,3655,4906,6414,8203,10297,12720,
%T 15496,18649,22203,26182,30610,35511,40909,46828,53292,60325,67951,
%U 76194,85078,94627,104865,115816,127504
%N Principal diagonal of the convolution array A213831.
%H Clark Kimberling, <a href="/A213832/b213832.txt">Table of n, a(n) for n = 1..1000</a>
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1).
%F G.f.: x*(1 + 15*x + 8*x^2)/(1-x)^4.
%F a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4).
%F a(n) = (n - 7*n^2 + 8*n^3)/2.
%F a(n) = Sum_{i = 0..n-1} (n + i)*(n + 3*i). - _Bruno Berselli_, Feb 14 2018
%t (See A213831.)
%Y Cf. A213831.
%K nonn,easy
%O 1,2
%A _Clark Kimberling_, Jul 04 2012
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