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 A154549 #40 Sep 15 2024 14:32:57
%S A154549 111111,222222,333333,444444,555555,666666,777777,888888,999999,
%T A154549 1111110,1222221,1333332,1444443,1555554,1666665,1777776,1888887,
%U A154549 1999998,2111109,2222220,2333331,2444442,2555553,2666664,2777775,2888886,2999997,3111108,3222219,3333330,3444441,3555552
%N A154549 a(n) = 111111*n.
%C A154549 This sequence was described by Magnitsky, Leontiy Filippovich (1669-1739), author of "The Russian Mathematical Encyclopedia" (1703) and other books. See the Kvant link. Magnitsky wrote it as a(n) = 143n*777. - _Oleg Zyakun_, Feb 28 2009
%H A154549 Vincenzo Librandi, <a href="/A154549/b154549.txt">Table of n, a(n) for n = 1..1000</a>
%H A154549 A. Zhukov, <a href="http://kvant.mccme.ru/pdf/1998/06/kv0698kaleid.pdf">Wonderful sequences</a>, Kvant 6, 1998. (in Russian)
%H A154549 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A154549 G.f.: 111111*x/(1-x)^2. - _Vincenzo Librandi_, Feb 29 2012
%F A154549 From _Elmo R. Oliveira_, Sep 15 2024: (Start)
%F A154549 E.g.f.: 111111*x*exp(x).
%F A154549 a(n) = a(n-1) + 111111 for n > 1.
%F A154549 a(n) = 2*a(n-1) - a(n-2) for n > 2. (End)
%t A154549 LinearRecurrence[{2, -1}, {111111, 222222}, 20] (* _Vincenzo Librandi_, Feb 28 2012 *)
%t A154549 111111Range[30] (* _Harvey P. Dale_, Aug 11 2016 *)
%o A154549 (PARI) a(n)=111111*n \\ _Charles R Greathouse IV_, Jan 11 2012
%K A154549 nonn,easy
%O A154549 1,1
%A A154549 _Vincenzo Librandi_, Jan 11 2009