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%I #19 Jun 13 2021 15:27:43
%S 0,15,55,120,210,325,465,630,820,1035,1275,1540,1830,2145,2485,2850,
%T 3240,3655,4095,4560,5050,5565,6105,6670,7260,7875,8515,9180,9870,
%U 10585,11325,12090,12880,13695,14535,15400,16290,17205,18145,19110,20100
%N a(n) = 5*n*(5*n + 1)/2.
%H Stefano Spezia, <a href="/A144312/b144312.txt">Table of n, a(n) for n = 0..10000</a>
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F a(n) = A000217(5*n).
%F a(n) = a(n-1) + 25*n - 10 (with a(0) = 0). - _Vincenzo Librandi_, Nov 25 2010
%F From _Stefano Spezia_, Jun 12 2021: (Start)
%F O.g.f.: 5*x*(3 + 2*x)/(1 - x)^3.
%F E.g.f.: 5*exp(x)*x*(6 + 5*x)/2.
%F a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 2. (End)
%o (PARI) a(n)=5*n*(5*n+1)/2 \\ _Charles R Greathouse IV_, Jun 17 2017
%Y Cf. A000217, A014105, A033585, A081266.
%K nonn,easy
%O 0,2
%A _Reinhard Zumkeller_, Sep 17 2008
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