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a(n) = (6*n + 3)^4.
9

%I #17 Mar 30 2022 06:34:19

%S 81,6561,50625,194481,531441,1185921,2313441,4100625,6765201,10556001,

%T 15752961,22667121,31640625,43046721,57289761,74805201,96059601,

%U 121550625,151807041,187388721,228886641,276922881,332150625,395254161,466948881,547981281,639128961

%N a(n) = (6*n + 3)^4.

%H Vincenzo Librandi, <a href="/A016948/b016948.txt">Table of n, a(n) for n = 0..2000</a>

%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1).

%F From _Amiram Eldar_, Mar 30 2022: (Start)

%F a(n) = A016945(n)^4 = A016946(n)^2.

%F a(n) = 3^4*A016756(n).

%F Sum_{n>=0} 1/a(n) = Pi^4/7776. (End)

%t a[n_] := (6*n + 3)^4; Array[a, 50, 0] (* _Amiram Eldar_, Mar 30 2022 *)

%o (Magma) [(6*n+3)^4: n in [0..50]]; // _Vincenzo Librandi_, May 05 2011

%Y Cf. A000583, A016756, A016945, A016946, A016947.

%K nonn,easy

%O 0,1

%A _N. J. A. Sloane_