%I A038507
%S A038507 2,2,3,7,25,121,721,5041,40321,362881,3628801,39916801,
%T A038507 479001601,6227020801,87178291201,1307674368001,20922789888001,
%U A038507 355687428096001,6402373705728001,121645100408832001
%N A038507 n! + 1.
%C A038507 "For n = 4, 5 and 7, n!+1 is a square. Sierpinski asked if there are 
               any other values of n with this property." p. 82 of Ogilvy and Anderson.
%C A038507 Number of {12,12*,1*2,21*,2*1}-avoiding signed permutations in the hyperoctahedral 
               group.
%D A038507 C. Stanley Ogilvy and John T. Anderson, Excursions in Number Theory, 
               Oxford University Press, 1966, p. 82.
%D A038507 Waclaw Sierpinski, On some unsolved problems of arithmetics, Scripta 
               Mathematica, vol. 25 (1960), p. 125.
%D A038507 Arthur T. White, Ringing the changes, Math. Proc. Cambridge Philos. Soc. 
               94 (1983), no. 2, 203-215.
%H A038507 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=763">
               Encyclopedia of Combinatorial Structures 763</a>
%H A038507 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=834">
               Encyclopedia of Combinatorial Structures 834</a>
%H A038507 T. Mansour and J. West, <a href="http://arXiv.org/abs/math.CO/0207204">
               Avoiding 2-letter signed patterns</a>.
%H A038507 G. P. Michon, <a href="http://home.att.net/~numericana/wilson.htm">Wilson's 
               Theorem</a>
%H A038507 Hisanori Mishima, <a href="http://www.asahi-net.or.jp/~KC2H-MSM/mathland/
               matha1/matha102.htm">Factorizations of many number sequences</a>
%H A038507 Hisanori Mishima, <a href="http://www.asahi-net.or.jp/~KC2H-MSM/mathland/
               matha1/matha104.htm">Factorizations of many number sequences</a>
%H A038507 Andrew Walker, <a href="http://www.uow.edu.au/~ajw01/ecm/curves.html">
               Factors of n! +- 1</a>
%H A038507 R. G. Wilson v, <a href="a38507.txt">Explicit factorizations</a>
%H A038507 <a href="Sindx_Fa.html#factorial">Index entries for sequences related 
               to factorial numbers</a>
%t A038507 f[n_]:=n!+1;lst={};Do[AppendTo[lst,f[n]],{n,0,5!}];lst [From Vladimir 
               Orlovsky (4vladimir(AT)gmail.com), Jun 27 2009]
%Y A038507 Cf. A000142, A033312.
%Y A038507 Cf. A002583; A051301; A056111; A002981.
%Y A038507 Sequence in context: A083701 A076996 A139148 this_sequence A077001 A087522 
               A092970
%Y A038507 Adjacent sequences: A038504 A038505 A038506 this_sequence A038508 A038509 
               A038510
%K A038507 nonn,easy,nice
%O A038507 0,1
%A A038507 N. J. A. Sloane (njas(AT)research.att.com).
%E A038507 Additional comments from Jason Earls (zevi_35711(AT)yahoo.com), Apr 01 
               2001