%I A002777 M3526 N1432
%S A002777 1,0,0,0,4,16,80,672,4896,49920,460032,5598720,62584320,885381120,
%T A002777 11644323840,187811205120,2841958748160,51481298534400,881192033648640,
%U A002777 17714783352913920,338434210452602880,7477275543168614400
%N A002777 Restricted permutations.
%D A002777 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A002777 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A002777 T. Muir, The Theory of Determinants in the Historical Order of Development. 
               4 vols., Macmillan, NY, 1906-1923, Vol. 3, p. 468.
%D A002777 Simpson, Todd; Permutations with unique fixed and reflected points. Ars 
               Combin. 39 (1995), 97-108.
%H A002777 T. Muir, <a href="http://www.hti.umich.edu/cgi/t/text/text-idx?sid=b88432273f115fb346725f1a42422e19;
               c=umhistmath;idno=ACM9350.0003.001">The Theory of Determinants in 
               the Historical Order of Development</a>, 4 vols., Macmillan, NY, 
               1906-1923, Vol. 2.
%F A002777 a(n) = (n-1)*a(n-1) + 2*(n-d)*a(n-e), where (d, e) = (2, 3) if n even, 
               (1, 2) if n odd.
%Y A002777 Sequence in context: A075581 A020080 A003471 this_sequence A118997 A001257 
               A133053
%Y A002777 Adjacent sequences: A002774 A002775 A002776 this_sequence A002778 A002779 
               A002780
%K A002777 nonn,easy
%O A002777 0,5
%A A002777 N. J. A. Sloane (njas(AT)research.att.com).
%E A002777 More terms from Larry Reeves (larryr(AT)acm.org), Sep 24 2001