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 A006323 #24 Dec 27 2022 16:29:42
%S A006323 1,10,41,115,260,511,910,1506,2355,3520,5071,7085,9646,12845,16780,
%T A006323 21556,27285,34086,42085,51415,62216,74635,88826,104950,123175,143676,
%U A006323 166635,192241,220690,252185,286936,325160,367081,412930
%N A006323 4-dimensional analog of centered polygonal numbers.
%H A006323 Vincenzo Librandi, <a href="/A006323/b006323.txt">Table of n, a(n) for n = 1..1000</a>
%H A006323 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5, -10, 10, -5, 1).
%F A006323 a(n) = 7*C(n + 2, 4) + C(n + 1, 2).
%F A006323 G.f.: x*(-1-x^2-5*x)/(x-1)^5. - Maksym Voznyy (voznyy(AT)mail.ru), Aug 10 2009; adapted to the offset by _Vincenzo Librandi_, Sep 06 2013
%F A006323 Sum_{n>=1} 1/a(n) = 30 + 4*sqrt(21/5)*Pi*tan(sqrt(15/7)*Pi/2). - _Amiram Eldar_, Aug 23 2022
%t A006323 CoefficientList[Series[(-1 - x^2 - 5 x) / (x - 1)^5, {x, 0, 40}],x] (* _Vincenzo Librandi_, Sep 06 2013 *)
%t A006323 LinearRecurrence[{5,-10,10,-5,1},{1,10,41,115,260},40] (* _Harvey P. Dale_, Dec 27 2022 *)
%o A006323 (PARI) a(n) = 7*binomial(n + 2, 4) + binomial(n + 1, 2); \\ _Michel Marcus_, Sep 05 2013
%o A006323 (Magma) [7*Binomial(n+2,4)+Binomial(n+1,2): n in [1..40]]; // _Vincenzo Librandi_, Sep 06 2013
%K A006323 nonn,easy
%O A006323 1,2
%A A006323 Albert Rich (Albert_Rich(AT)msn.com)