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 A241858 #19 Aug 11 2020 12:54:07
%S A241858 1,3,6,10,11,13,14,17,19,21,24,26,28,29,34,36,38,40,42,44,48,51,54,57,
%T A241858 58,61,62,65,66,69,72,73,76,79,80,83,85,88,89,91,92,96,97,100,102,104,
%U A241858 105,109,115,119,121,124,130,133,140,141,144,149,150,154,159,161,164,169
%N A241858 Positions of vowels in "one, two, three, four, five, six, ...".
%C A241858 Consider only letters, but not spaces or punctuation.
%H A241858 M. F. Hasler, <a href="/A241858/b241858.txt">Table of n, a(n) for n = 1..10^4</a>
%e A241858 The letters in "four" are the twelfth through fifteenth letters in "one, two, three, four, five, six, ...". The o and u, which are 13 and 14, are vowels.
%o A241858 (PARI) A241858_vec(N,v=Vec("aeiou"),n,s,p,o)=vector(N,j, until( setsearch(v,s[p-o]), o+#s<p++ && o+=#s+!s=[c|c<-Vec(English(n+=1)),c>"@"]); p) \\ see A052360 for English(). - _M. F. Hasler_, Aug 11 2020
%Y A241858 Cf. A005589, A052360.
%K A241858 nonn,word
%O A241858 1,2
%A A241858 _J. Lowell_, Apr 30 2014
%E A241858 More terms from _Alois P. Heinz_, Apr 30 2014
%E A241858 a(62)-a(64) from _M. F. Hasler_, Aug 11 2020