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 A147816 #19 Mar 08 2024 01:12:29
%S A147816 1,1100,1110000,1111000000,1111100000000,1111110000000000,
%T A147816 1111111000000000000,1111111100000000000000,1111111110000000000000000,
%U A147816 1111111111000000000000000000,1111111111100000000000000000000,1111111111110000000000000000000000
%N A147816 Concatenation of n digits 1 and 2(n-1) digits 0.
%C A147816 a(n) is also A016152(n) written in base 2.
%H A147816 Paolo Xausa, <a href="/A147816/b147816.txt">Table of n, a(n) for n = 1..300</a>
%H A147816 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (1100,-100000).
%F A147816 a(n) = A138119(n)/10.
%F A147816 a(n) = 1100*a(n-1)-100000*a(n-2). G.f.: x / ((100*x-1)*(1000*x-1)). - _Colin Barker_, Sep 16 2013
%e A147816 n ...... a(n)
%e A147816 1 ....... 1
%e A147816 2 ...... 1100
%e A147816 3 ..... 1110000
%e A147816 4 .... 1111000000
%e A147816 5 ... 1111100000000
%t A147816 Array[(10^#-1)*10^(2*#-2)/9 &, 20] (* or *)
%t A147816 LinearRecurrence[{1100, -100000}, {1, 1100}, 20] (* Paolo Xausa, Feb 27 2024 *)
%o A147816 (PARI) Vec(x/((100*x-1)*(1000*x-1)) + O(x^100)) \\ _Colin Barker_, Sep 16 2013
%Y A147816 Cf. A000533, A016152, A135577, A138119, A138120, A138144, A138145, A138146, A138721, A138826, A147757, A147759.
%K A147816 base,easy,nonn
%O A147816 1,2
%A A147816 _Omar E. Pol_, Nov 13 2008