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 A244663 #24 Sep 08 2022 08:46:08 %S A244663 111,10111,1001111,100011111,10000111111,1000001111111, %T A244663 100000011111111,10000000111111111,1000000001111111111, %U A244663 100000000011111111111,10000000000111111111111,1000000000001111111111111,100000000000011111111111111,10000000000000111111111111111 %N A244663 Binary representation of 4^n + 2^(n+1) - 1. %H A244663 Colin Barker, <a href="/A244663/b244663.txt">Table of n, a(n) for n = 1..450</a> %H A244663 Wikipedia, <a href="https://en.wikipedia.org/wiki/Kynea_number">Kynea number</a> %H A244663 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (111,-1110,1000). %F A244663 a(n) = -1/9+10^(1+n)/9+100^n. %F A244663 a(n) = 111*a(n-1)-1110*a(n-2)+1000*a(n-3). %F A244663 G.f.: -x*(2000*x^2-2210*x+111) / ((x-1)*(10*x-1)*(100*x-1)). %e A244663 a(3) is 1001111 because A093069(3) = 79 which is 1001111 in base 2. %p A244663 A244663:=n->-1/9+10^(1+n)/9+100^n: seq(A244663(n), n=1..15); # _Wesley Ivan Hurt_, Jul 09 2014 %t A244663 Table[-1/9 + 10^(1 + n)/9 + 100^n, {n, 15}] (* _Wesley Ivan Hurt_, Jul 09 2014 *) %t A244663 LinearRecurrence[{111,-1110,1000},{111,10111,1001111},20] (* _Harvey P. Dale_, Dec 11 2014 *) %o A244663 (PARI) vector(100, n, -1/9+10^(1+n)/9+100^n) %o A244663 (PARI) Vec(-x*(2000*x^2-2210*x+111)/((x-1)*(10*x-1)*(100*x-1)) + O(x^100)) %o A244663 (Magma) [-1/9 + 10^(1 + n)/9 + 100^n : n in [1..15]]; // _Wesley Ivan Hurt_, Jul 09 2014 %Y A244663 Cf. A093069. %K A244663 nonn,easy,base %O A244663 1,1 %A A244663 _Colin Barker_, Jul 08 2014