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 A099971 #15 Aug 02 2025 17:04:07
%S A099971 1,9,25,57,121,1145,3193,11385,27769,60537,191609,453753,978041,
%T A099971 2026617,10415225,27192441,94301305,228519033,496954489,2644438137,
%U A099971 11234372729,28414241913,62773980281,131493457017,268932410489,543810317433
%N A099971 Write (sqrt(5)-1)/2 as a binary fraction; read this from left to right and whenever a 1 appears, note the integer formed by reading leftwards from that 1.
%e A099971 (sqrt(5)-1)/2 = 0.618033988749894848204586834365638117720309179805762862135... = 0.100111100011011101111001101110010111111101001010011111000001010111110011... in binary.
%t A099971 d = 100; l = First[RealDigits[N[(Sqrt[5]-1)/2, d], 2]]; Do[m = Take[l, n]; k = Length[m]; If[m[[k]] == 1, Print[FromDigits[Reverse[m], 2]]], {n, 1, d}] (* _Ryan Propper_, Aug 18 2005 *)
%Y A099971 Cf. A094214, A099969, A099970, A099972, A099973, A099974.
%K A099971 nonn,easy
%O A099971 0,2
%A A099971 _N. J. A. Sloane_, Nov 13 2004, based on correspondence from _Artur Jasinski_, Mar 25 2003
%E A099971 More terms from _Ryan Propper_, Aug 18 2005