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%I #8 Nov 04 2024 09:30:51
%S 11,105,923,7761,63731,516825,4163723,33429921,267930851,2145445545,
%T 17171657723,137405930481,1099379004371,8795560934265,70366611042923,
%U 562941406533441,4503565396772291,36028659967430985,288229827558159323,2305840813677222801
%N a(n) = 3^n + 2^(3*n + 1) - 2^(2*n + 1).
%C Also number of edge cuts in the n-book graph.
%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/BookGraph.html">Book Graph</a>.
%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/EdgeCut.html">Edge Cut</a>.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (15,-68,96).
%F a(n) = 15*a(n-1)-68*a(n-2)+96*a(n-3).
%F G.f.: x*(-11+60*x-96*x^2)/(-1+15*x-68*x^2+96*x^3).
%t Table[3^n + 2^(3 n + 1) - 2^(2 n + 1), {n, 20}]
%t LinearRecurrence[{15, -68, 96}, {11, 105, 923}, 20]
%t CoefficientList[Series[-(11 - 60 x + 96 x^2)/((-1 + 3 x) (-1 + 4 x) (-1 + 8 x)), {x, 0, 20}], x]
%o (Python)
%o def A377641(n): return 3**n+(2<<3*n)-(2<<(n<<1)) # _Chai Wah Wu_, Nov 03 2024
%K nonn,easy
%O 1,1
%A _Eric W. Weisstein_, Nov 03 2024