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 A047668 #18 Jul 05 2024 10:48:45
%S A047668 4,17,52,129,276,529,932,1537,2404,3601,5204,7297,9972,13329,17476,
%T A047668 22529,28612,35857,44404,54401,66004,79377,94692,112129,131876,154129,
%U A047668 179092,206977,238004,272401,310404,352257,398212,448529
%N A047668 Row 4 of array in A047666.
%C A047668 In this sequence if we do a forward difference, then the 3rd forward difference when considered as a sequence will be an arithmetic progression with common difference 8. [Gopalakrishnan (gopala498(AT)yahoo.co.in), Jun 05 2010]
%H A047668 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5, -10, 10, -5, 1).
%F A047668 a(n) = (1/3) * (n^4 + 8n^2 + 3).
%F A047668 G.f.: x*(4 - 3*x + 7*x^2 - x^3 + x^4)/(1-x)^5. - Maksym Voznyy (voznyy(AT)mail.ru), Jul 27 2009 [corrected by _R. J. Mathar_, Sep 16 2009]
%t A047668 LinearRecurrence[{5,-10,10,-5,1},{4,17,52,129,276},40] (* _Harvey P. Dale_, Jul 05 2024 *)
%K A047668 nonn
%O A047668 1,1
%A A047668 _N. J. A. Sloane_