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 A045510 #19 Jul 19 2020 02:11:49
%S A045510 2,24,20922789888000,2432902008176640000,25852016738884976640000,
%T A045510 265252859812191058636308480000000,
%U A045510 263130836933693530167218012160000000
%N A045510 Factorials having initial digit '2'.
%C A045510 Benford's law shows that this sequence will contain about (log 3 - log 2)/log 10 =~ 18% of factorials. [_Charles R Greathouse IV_, Nov 13 2010]
%F A045510 a(n) = A000142(A045521(n)). - _Amiram Eldar_, Jul 19 2020
%t A045510 Select[Range[50]!,IntegerDigits[#][[1]]==2&] (* _Harvey P. Dale_, Mar 21 2020 *)
%o A045510 (PARI) lista(nn) = {for (n=1, nn, if (digits(n!)[1] == 2, print1(n!, ", ")););} \\ _Michel Marcus_, Dec 13 2017
%Y A045510 For factorials with initial digit d (1 <= d <= 9) see A045509, A045510, A045511, A045516, A045517, A045518, A282021, A045519; A045520, A045521, A045522, A045523, A045524, A045525, A045526, A045527, A045528, A045529.
%Y A045510 Cf. A000142.
%K A045510 nonn,base
%O A045510 1,1
%A A045510 _Jeff Burch_