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 A102439 #29 Jun 09 2025 21:01:51
%S A102439 4,104,204,304,404,504,604,704,804,904,1004,1104,1204,1304,1404,1504,
%T A102439 1604,1704,1804,1904,2004,2104,2204,2304,2404,2504,2604,2704,2804,
%U A102439 2904,3004,3104,3204,3304,3404,3504,3604,3704,3804,3904,4004,4104,4204,4304,4404,4504
%N A102439 a(n) = 100*n + 4.
%H A102439 Vincenzo Librandi, <a href="/A102439/b102439.txt">Table of n, a(n) for n = 0..5000</a>
%H A102439 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>.
%H A102439 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A102439 G.f.: 4*(1+24*x)/(-1+x)^2. - _Harvey P. Dale_, Aug 30 2021
%F A102439 From _Elmo R. Oliveira_, Jun 09 2025: (Start)
%F A102439 E.g.f.: 4*exp(x)*(1 + 25*x).
%F A102439 a(n) = 4*A158060(n) for n > 0.
%F A102439 a(n) = 2*a(n-1) - a(n-2). (End)
%t A102439 100 Range[0,40]+4 (* or *) LinearRecurrence[{2,-1},{4,104},50] (* _Harvey P. Dale_, Aug 30 2021 *)
%o A102439 (Magma)[100*n+4: n in [0..50]]; // _Vincenzo Librandi_, Jun 04 2011
%o A102439 (PARI) a(n)=100*n+4 \\ _Charles R Greathouse IV_, Jun 05 2011
%Y A102439 Cf. A158060.
%K A102439 easy,nonn
%O A102439 0,1
%A A102439 _Giovanni Teofilatto_, Feb 23 2005
%E A102439 Edited by _N. J. A. Sloane_, Jan 31 2009