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a(n) = (11*n+1)*(11*n+10).
2

%I #29 Oct 25 2024 08:25:59

%S 10,252,736,1462,2430,3640,5092,6786,8722,10900,13320,15982,18886,

%T 22032,25420,29050,32922,37036,41392,45990,50830,55912,61236,66802,

%U 72610,78660,84952,91486,98262,105280,112540,120042,127786,135772,144000,152470,161182,170136

%N a(n) = (11*n+1)*(11*n+10).

%H T. D. Noe, <a href="/A001536/b001536.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).

%F a(n) = 242*n + a(n-1) with a(0)=10. - _Vincenzo Librandi_, Nov 12 2010

%F G.f.: -2*(5+111*x+5*x^2)/(x-1)^3. - _R. J. Mathar_, May 30 2022

%F From _Amiram Eldar_, Feb 20 2023: (Start)

%F a(n) = A017401(n)*A017509(n).

%F Sum_{n>=0} 1/a(n) = cot(Pi/11)*Pi/99.

%F Product_{n>=0} (1 - 1/a(n)) = cosec(Pi/11)*cos(sqrt(85)*Pi/22).

%F Product_{n>=0} (1 + 1/a(n)) = cosec(Pi/11)*cos(sqrt(77)*Pi/22). (End)

%F From _Elmo R. Oliveira_, Oct 25 2024: (Start)

%F E.g.f.: exp(x)*(10 + 121*x*(2 + x)).

%F a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 2.

%t Table[(11*n + 1)*(11*n + 10), {n, 0, 40}] (* _Amiram Eldar_, Feb 20 2023 *)

%o (PARI) a(n)=(11*n+1)*(11*n+10) \\ _Charles R Greathouse IV_, Jun 16 2017

%Y Cf. A017401, A017509.

%K nonn,easy

%O 0,1

%A _N. J. A. Sloane_