%I A006347 M3018
%S A006347 0,1,3,16,95,666,5327,47944,479439,5273830,63285959,822717468,
%T A006347 11518044551,172770668266,2764330692255,46993621768336,845885191830047,
%U A006347 16071818644770894,321436372895417879,6750163830803775460
%N A006347 a(n) = (n+1) a(n-1) + (-1)^n.
%D A006347 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%F A006347 E.g.f.: x(1-x/2-exp(-x))/(1-x)^2. a(n)=n(a(n-1)+a(n-2)), n>2.
%F A006347 a(n)=round((1/2-exp(-1))*(n+1)!) - Benoit Cloitre (abmt(AT)orange.fr), 
               Sep 24 2006
%p A006347 a:=n->-n!*sum((-1)^k/k!, k=3..n): seq(a(n), n=2..21); - Zerinvary Lajos 
               (zerinvarylajos(AT)yahoo.com), May 25 2007
%o A006347 (PARI) a(n)=if(n<2,0,(n+1)*a(n-1)+(-1)^n)
%o A006347 (PARI) a(n)=round((1/2-exp(-1))*(n+1)!) - Benoit Cloitre (abmt(AT)orange.fr), 
               Sep 24 2006
%Y A006347 Sequence in context: A074555 A137644 A114174 this_sequence A000270 A157051 
               A000271
%Y A006347 Adjacent sequences: A006344 A006345 A006346 this_sequence A006348 A006349 
               A006350
%K A006347 nonn,easy
%O A006347 1,3
%A A006347 N. J. A. Sloane (njas(AT)research.att.com).