This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A287826 #10 May 22 2025 10:21:46
%S A287826 1,10,84,708,5968,50308,424080,3574860,30134944,254028100,2141377008,
%T A287826 18051134892,152165391616,1282706408548,10812811724688,91148603152524,
%U A287826 768354066287200,6476983198439812,54598931916359472,460251829451302764,3879778213203474880
%N A287826 Number of sequences over the alphabet {0,1,...,9} such that no two consecutive terms have distance 2.
%H A287826 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (10, -13, -2).
%F A287826 a(n) = 10*a(n-1) - 13*a(n-2) - 2a(n-3), a(0)=1, a(1)=10, a(2)=84.
%F A287826 G.f.: (1 - 3 x^2)/(1 - 10 x + 13 x^2 + 2 x^3).
%t A287826 LinearRecurrence[{10, -13, -2}, {1, 10, 84}, 40]
%o A287826 (Python)
%o A287826 def a(n):
%o A287826 if n in [0, 1, 2]:
%o A287826 return [1, 10, 84][n]
%o A287826 return 10*a(n-1)-13*a(n-2)-2*a(n-3)
%Y A287826 Cf. A040000, A003945, A083318, A078057, A003946, A126358, A003946, A055099, A003947, A015448, A126473. A287804-A287819. A287825-A287831.
%K A287826 nonn,easy
%O A287826 0,2
%A A287826 _David Nacin_, Jun 02 2017