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 A097321 #29 Feb 21 2025 05:19:05
%S A097321 24,210,720,1716,3360,5814,9240,13800,19656,26970,35904,46620,59280,
%T A097321 74046,91080,110544,132600,157410,185136,215940,249984,287430,328440,
%U A097321 373176,421800,474474,531360,592620,658416,728910,804264,884640,970200,1061106,1157520
%N A097321 a(n) = (3*n-1) * 3*n * (3*n+1).
%H A097321 Vincenzo Librandi, <a href="/A097321/b097321.txt">Table of n, a(n) for n = 1..10000</a>
%H A097321 S. Ramanujan, <a href="http://www.imsc.res.in/~rao/ramanujan/NoteBooks/NoteBook2/chapterII/page2.htm">Notebook entry</a>.
%H A097321 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1).
%F A097321 G.f.: 6x * (4x^2 + 19x + 4) / (1-x)^4.
%F A097321 Sum_{n>=1} 1/a(n) = (log(3) - 1)/2. - _Amiram Eldar_, Jul 04 2020
%F A097321 Sum_{n>=1} (-1)^(n+1)/a(n) = 1/2 - 2*log(2)/3. - _Amiram Eldar_, May 15 2022
%F A097321 E.g.f.: 3*exp(x)*x*(8 + 27*x + 9*x^2). - _Stefano Spezia_, Feb 20 2025
%t A097321 Table[27n^3-3n,{n,40}] (* _Harvey P. Dale_, Mar 30 2011 *)
%o A097321 (Magma) [27*n^3-3*n: n in [1..40]]; // _Vincenzo Librandi_, Sep 07 2011
%Y A097321 Cf. A069072, A069140, A002391, A016767.
%K A097321 nonn,easy
%O A097321 1,1
%A A097321 _Ralf Stephan_, Aug 07 2004