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 A079714 #23 Jun 20 2021 18:24:04
%S A079714 0,0,1,0,1,1,1,0,1,1,1,0,0,3,2,0,3,1,2,2,3,1,2,2,2,1,2,1,0,0,4,7,3,1,
%T A079714 4,3,3,3,7,4,5,4,3,4,4,4,8,6,6,10,3,10,3,6,9,6,1,9,10,6,9,10,13,8,6,
%U A079714 11,8,8,8,14,7,8,10,8,14,9,12,10,16,8,12,9,5,9,12,14,17,16,12,9,10,8,8,17,11,19,7,13,16,19,19,14
%N A079714 Number of 2's in n!.
%H A079714 Alois P. Heinz, <a href="/A079714/b079714.txt">Table of n, a(n) for n = 0..10000</a>
%H A079714 <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>.
%F A079714 a(n) = A034886(n) - (A027869(n) + A079680(n) + A079684(n) + A079688(n) + A079690(n) + A079691(n) + A079692(n) + A079693(n) + A079694(n)). - _Reinhard Zumkeller_, Jan 27 2008
%p A079714 a:= n-> numboccur(2, convert(n!, base, 10)):
%p A079714 seq(a(n), n=0..101); # _Alois P. Heinz_, Apr 26 2021
%t A079714 Table[DigitCount[n!,10,2],{n,0,110}] (* _Harvey P. Dale_, Jun 20 2021 *)
%o A079714 (PARI) a(n) = #select(x->(x==2), digits(n!)); \\ _Michel Marcus_, Apr 26 2021
%Y A079714 Cf. A000142, A137579, A137580.
%Y A079714 Cf. A316863.
%K A079714 nonn,base,easy
%O A079714 0,14
%A A079714 _Cino Hilliard_, Jan 31 2003
%E A079714 a(36) ff. corrected by _Georg Fischer_, Apr 26 2021