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A165187 a(n) = n^3*(n+1)^2*(n+2)/12. 1

%I #17 Feb 13 2023 08:59:19

%S 1,24,180,800,2625,7056,16464,34560,66825,121000,207636,340704,538265,

%T 823200,1224000,1775616,2520369,3508920,4801300,6468000,8591121,

%U 11265584,14600400,18720000,23765625,29896776,37292724,46154080,56704425,69192000,83891456,101105664

%N a(n) = n^3*(n+1)^2*(n+2)/12.

%C a(n) is row 30 of Table A128629 and can be generated by multiplying rows

%C two, three and five (or any other combination of rows with a row number product of 30).

%H <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (7,-21,35,-35,21,-7,1).

%F a(n) = A000027(n)*A000217(n)*A000292(n) = A128629(30,n).

%F a(n) = 7*a(n-1)-21*a(n-2)+35*a(n-3)-35*a(n-4)+21*a(n-5)-7*a(n-6)+a(n-7).

%F G.f.: -x*(1+17*x+33*x^2+9*x^3)/(x-1)^7.

%F From _Amiram Eldar_, Feb 13 2023: (Start)

%F Sum_{n>=1} 1/a(n) = 153/4 - 9*Pi^2/2 + 6*zeta(3).

%F Sum_{n>=1} (-1)^(n+1)/a(n) = 48*log(2) - 141/4 - Pi^2/4 + 9*zeta(3)/2. (End)

%e 1,2,3,4,5, ... (A000027) times 1,3,6,10,15, ... (A000217) times 1,4,10,20,35, ... (A000292) yields 1,24,180,800, ...

%t a[n_] := n^3*(n+1)^2*(n+2)/12; Array[a, 35] (* _Amiram Eldar_, Feb 13 2023 *)

%Y Cf. A000027, A000217, A000292, A128629.

%K nonn,easy

%O 1,2

%A _Alford Arnold_, Sep 06 2009

%E Edited and extended by _R. J. Mathar_, Sep 09 2009

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Last modified March 28 16:58 EDT 2024. Contains 371254 sequences. (Running on oeis4.)