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 A065892 #18 Aug 10 2024 03:54:43
%S A065892 0,0,2,14,89,591,4364,36088,331910,3370110,37487843,453695312,
%T A065892 5937400048,83567800394,1258987455069,20216786089860,344733810100259,
%U A065892 6221338673520239,118470005905053478,2374008406467087461,49939116469530531211,1100312192659475223331,25340966583568917929966
%N A065892 Which composite number is n! ?: a(n) = k such that A002808(k) = n!, or 0 if n! is not composite.
%H A065892 Amiram Eldar, <a href="/A065892/b065892.txt">Table of n, a(n) for n = 1..25</a> (calculated using the data at A003604)
%F A065892 a(n) = n! - A003604(n) - 1. - _Amiram Eldar_, Aug 09 2024
%e A065892 For n = 4: 4! = 24 = A002808(14) is the 14th composite number.
%t A065892 Table[n! - PrimePi[n!] - 1, {n, 1, 12}]
%o A065892 (PARI) a(n) = my(f = n!); f - primepi(f) - 1; \\ _Amiram Eldar_, Aug 09 2024
%Y A065892 Cf. A000142, A002808, A003604.
%K A065892 nonn
%O A065892 1,3
%A A065892 _Labos Elemer_, Nov 28 2001
%E A065892 More terms from _Robert G. Wilson v_, Nov 29 2001
%E A065892 Name clarified and a(17)-a(23) from _Amiram Eldar_, Aug 09 2024