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 A099970 #23 Aug 02 2025 17:05:05
%S A099970 1,5,13,29,61,573,2621,6717,23101,88637,350781,875069,9263677,
%T A099970 26040893,93149757,227367485,2374851133,10964785725,28144654909,
%U A099970 165583608381,440461515325,990217329213,3189240584765,7587287095869,16383380118077
%N A099970 Write 1/e 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. Then convert those integers from binary into decimal numbers.
%H A099970 Harvey P. Dale, <a href="/A099970/b099970.txt">Table of n, a(n) for n = 0..1000</a>
%F A099970 a(n) = A099969(n)/2. - _Michel Marcus_, Nov 03 2013
%e A099970 1/e = 0.367879441171442321595523770161460867445811131031767834507... = 0.010111100010110101011000110110001011001110111100110111110001101010111010110111 in binary.
%t A099970 d = 100; l = First[RealDigits[N[1/E, 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 *)
%t A099970 Module[{nn=50,e},e=RealDigits[1/E,2, 50][[1]];Table[If[e[[n]]== 0, Nothing,FromDigits[ Reverse[Take[e,n]],2]],{n,nn}]] (* _Harvey P. Dale_, Sep 17 2020 *)
%Y A099970 Cf. A068985, A099969, A099971, A099972, A099973, A099974.
%K A099970 nonn,easy
%O A099970 0,2
%A A099970 _N. J. A. Sloane_, Nov 13 2004, based on correspondence from _Artur Jasinski_, Mar 25 2003
%E A099970 More terms from _Ryan Propper_, Aug 18 2005
%E A099970 Definition amended by _Harvey P. Dale_, Sep 17 2020