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 A047673 #13 Sep 01 2025 03:03:40
%S A047673 1,13,61,193,481,1021,1933,3361,5473,8461,12541,17953,24961,33853,
%T A047673 44941,58561,75073,94861,118333,145921,178081,215293,258061,306913,
%U A047673 362401,425101,495613,574561,662593,760381,868621,988033,1119361,1263373,1420861,1592641,1779553
%N A047673 Row 4 of square array defined in A047671.
%H A047673 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1).
%F A047673 a(n) = n^4 - 2*n^3 + 5*n^2 - 4*n + 1.
%F A047673 From _Elmo R. Oliveira_, Aug 30 2025: (Start)
%F A047673 G.f.: -x*(1 + 8*x + 6*x^2 + 8*x^3 + x^4)/(x-1)^5.
%F A047673 E.g.f.: -1 + (1 + 6*x^2 + 4*x^3 + x^4)*exp(x).
%F A047673 a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n > 5. (End)
%o A047673 (PARI) my(x='x+O('x^38)); Vec(x*(1+8*x+6*x^2+8*x^3+x^4)/(1-x)^5) \\ _Elmo R. Oliveira_, Aug 30 2025
%Y A047673 Cf. A047671.
%K A047673 nonn,easy,changed
%O A047673 1,2
%A A047673 _N. J. A. Sloane_
%E A047673 More terms from _Elmo R. Oliveira_, Aug 30 2025