0,1

"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.

Number of {12,12*,1*2,21*,2*1}-avoiding signed permutations in the hyperoctahedral group.

C. Stanley Ogilvy and John T. Anderson, Excursions in Number Theory, Oxford University Press, 1966, p. 82.

Waclaw Sierpinski, On some unsolved problems of arithmetics, Scripta Mathematica, vol. 25 (1960), p. 125.

Arthur T. White, Ringing the changes, Math. Proc. Cambridge Philos. Soc. 94 (1983), no. 2, 203-215.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 763

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 834

T. Mansour and J. West, Avoiding 2-letter signed patterns.

G. P. Michon, Wilson's Theorem

Hisanori Mishima, Factorizations of many number sequences

Hisanori Mishima, Factorizations of many number sequences

Andrew Walker, Factors of n! +- 1

R. G. Wilson v, Explicit factorizations

Index entries for sequences related to factorial numbers

f[n_]:=n!+1; lst={}; Do[AppendTo[lst, f[n]], {n, 0, 5!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Jun 27 2009]

Cf. A000142, A033312.

Cf. A002583; A051301; A056111; A002981.

Adjacent sequences: A038504 A038505 A038506 this_sequence A038508 A038509 A038510

Sequence in context: A083701 A076996 A139148 this_sequence A077001 A087522 A092970

nonn,easy,nice

N. J. A. Sloane (njas(AT)research.att.com).

Additional comments from Jason Earls (zevi_35711(AT)yahoo.com), Apr 01 2001