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 A055490 #36 Jul 16 2025 13:36:42 %S A055490 5,23,719,5039,479001599,87178291199, %T A055490 265252859812191058636308479999999, %U A055490 263130836933693530167218012159999999,8683317618811886495518194401279999999 %N A055490 Factorial primes: primes of the form n! - 1. %C A055490 For further information see A002982, which is the main entry. %C A055490 Also primes of the form 1*1! + 2*2! + ... + n*n!. - _Jonathan Vos Post_, Jul 21 2006 %C A055490 Prime numbers that are the difference of two factorial numbers. - _Juri-Stepan Gerasimov_, Nov 08 2010 %D A055490 James J. Tattersall, Elementary Number Theory in Nine Chapters, Cambridge University Press, 1999, page 118. %H A055490 T. D. Noe, <a href="/A055490/b055490.txt">Table of n, a(n) for n=1..12</a> %F A055490 p = n!-1 for some n given in A002982. %t A055490 Select[Range[40]!-1,PrimeQ] (* _Harvey P. Dale_, Aug 16 2012 *) %Y A055490 Cf. A000142, A000203, A002982. %K A055490 nonn %O A055490 1,1 %A A055490 _Labos Elemer_, Jun 28 2000 %E A055490 Edited by _Jon E. Schoenfield_, Jan 09 2015