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 A164794 #11 Feb 02 2021 22:46:57
%S A164794 4,-1,15,-1,-1,44,24,74,-1,-1,104,404,115,415,315,144,124,174,324,374,
%T A164794 3074,1104,1404,1115,1415,1315,1144,1124,1174,1324,1374,3324,3374,
%U A164794 11374,13324,13374,17374,23324,23374,73374,101374,103324,103374,111374,113324
%N A164794 a(n) is the smallest number whose English name has the letter "f" in the n-th position, or -1 if no such number exists.
%e A164794 a(1)=4 ("Four"), a(3)=15 ("fiFteen"), a(11)=104 ("onehundredFour").
%Y A164794 Cf. A164789 ("o"), A164790 ("e"), A164791 ("n"), A164792 ("t").
%Y A164794 Cf. A164793 ("i"), A164795 ("h"), A164796 ("r"), A164797 ("u").
%K A164794 word,sign
%O A164794 1,1
%A A164794 _Claudio Meller_, Aug 26 2009
%E A164794 a(21) and beyond from _Michael S. Branicky_, Feb 02 2021