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%I #18 Jan 03 2021 16:55:11
%S 21,165,437,837,1365,2021,2805,3717,4757,5925,7221,8645,10197,11877,
%T 13685,15621,17685,19877,22197,24645,27221,29925,32757,35717,38805,
%U 42021,45365,48837,52437,56165,60021,64005,68117,72357,76725,81221
%N a(n) = (8*n+3)*(8*n+7).
%C Sum_{n>=0} 1/((8*n+3)*(8*n+7)) = (1/16)*sqrt(2)*(log(sqrt(2)-1) + Pi/2) = 0.60936936799920131042...
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F G.f: (21 + 102*x + 5*x^2)/(1-x)^3.
%F E.g.f.: (21 + 144*x + 64*x^2)*exp(x).
%p seq((8*n+3)*(8*n+7),n=0..40);
%t Table[(8n+3)(8n+7),{n,0,40}] (* or *) LinearRecurrence[{3,-3,1},{21,165,437},40] (* _Harvey P. Dale_, Aug 16 2015 *)
%o (PARI) a(n)=(8*n+3)*(8*n+7) \\ _Charles R Greathouse IV_, Jun 17 2017
%K nonn,easy
%O 0,1
%A _Miklos Kristof_, Oct 29 2008
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