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 A241848 #23 Jan 18 2025 13:31:28
%S A241848 18,19,22,27,34,43,54,67,82,99,118,139,162,187,214,243,274,307,342,
%T A241848 379,418,459,502,547,594,643,694,747,802,859,918,979,1042,1107,1174,
%U A241848 1243,1314,1387,1462,1539,1618,1699,1782,1867,1954,2043,2134,2227,2322,2419,2518
%N A241848 a(n) = n^2 + 18.
%H A241848 Vincenzo Librandi, <a href="/A241848/b241848.txt">Table of n, a(n) for n = 0..1000</a>
%H A241848 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A241848 G.f.: (18 - 35*x + 19*x^2)/(1 - x)^3.
%F A241848 a(n) = a(-n) = 3*a(n-1) - 3*a(n-2) + a(n-3) = a(n-1) + 2*n - 1.
%F A241848 From _Amiram Eldar_, Nov 03 2020: (Start)
%F A241848 Sum_{n>=0} 1/a(n) = (1 + sqrt(18)*Pi*coth(sqrt(18)*Pi))/36.
%F A241848 Sum_{n>=0} (-1)^n/a(n) = (1 + sqrt(18)*Pi*cosech(sqrt(18)*Pi))/36. (End)
%F A241848 E.g.f.: exp(x)*(18 + x + x^2). - _Elmo R. Oliveira_, Nov 29 2024
%t A241848 Table[n^2 + 18, {n, 0, 60}]
%t A241848 LinearRecurrence[{3,-3,1},{18,19,22},60] (* _Harvey P. Dale_, Jan 18 2025 *)
%o A241848 (Magma) [n^2+18: n in [0..60]];
%o A241848 (PARI) a(n)=n^2+18 \\ _Charles R Greathouse IV_, Jun 17 2017
%Y A241848 Cf. similar sequences listed in A114962.
%K A241848 nonn,easy
%O A241848 0,1
%A A241848 _Vincenzo Librandi_, May 01 2014