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 A180516 #29 Aug 27 2024 16:51:57
%S A180516 0,1,2,3,7,11,15,31,47,63,127,191,255,511,767,1023,2047,3071,4095,
%T A180516 8191,12287,16383,32767,49151,65535,131071,196607,262143,524287,
%U A180516 786431,1048575,2097151,3145727,4194303,8388607,12582911,16777215,33554431,50331647,67108863,134217727,201326591,268435455,536870911,805306367,1073741823,2147483647,3221225471
%N A180516 Numbers of the form i*4^j-1 (i=1..3, j >= 0).
%H A180516 Paolo Xausa, <a href="/A180516/b180516.txt">Table of n, a(n) for n = 1..1000</a>
%H A180516 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,4,-4).
%F A180516 From _Colin Barker_, Feb 01 2013: (Start)
%F A180516 a(n) = a(n-1) + 4*a(n-3) - 4*a(n-4).
%F A180516 G.f.: x^2*(x^2+x+1) / ((x-1)*(4*x^3-1)). (End)
%t A180516 LinearRecurrence[{1, 0, 4, -4}, Range[0, 3], 50] (* _Paolo Xausa_, Aug 27 2024 *)
%Y A180516 Smallest number whose base b sum of digits is n: A000225 (b=2), A062318 (b=3), this sequence (b=4), A181287 (b=5), A181288 (b=6), A181303 (b=7), A165804 (b=8), A140576 (b=9), A051885 (b=10). - _Jason Kimberley_, Nov 02 2011
%K A180516 nonn,easy
%O A180516 1,3
%A A180516 _N. J. A. Sloane_, Jan 25 2011