%I A052169
%S A052169 1,2,5,19,91,531,3641,28673,254871,2523223,27526069,328018989,
%T A052169 4239014627,59043418019,881715042417,14052333488521,238063061452591,
%U A052169 4271909380510383,80941440893880941,1614781745832924773
%N A052169 Equivalent of the Kurepa hypothesis for left factorial.
%C A052169 a(n)=A002467(n)/(n-1) (A002467(n)=number of non-derangements of {1,2,
               ...,n}). [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 15 
               2009]
%H A052169 Alexsandar Petojevic, <a href="http://www.cs.uwaterloo.ca/journals/JIS/
               index.html">The Function vM_m(s; a; z) and Some Well-Known Sequences</
               a>, Journal of Integer Sequences, Vol. 5 (2002), Article 02.1.7
%F A052169 a(2) = 1, a(3) = 2, a(n) = (n-2)*a(n-1) + (n-3)*a(n-2)
%p A052169 a[2] := 1: a[3] := 2: for n from 4 to 21 do a[n] := (n-2)*a[n-1]+(n-3)*a[n-2] 
               end do: seq(a[n], n = 2 .. 21); [From Emeric Deutsch (deutsch(AT)duke.poly.edu), 
               Jun 15 2009]
%t A052169 Numerator[k=1; NestList[1+1/(k++ #1)&,1,12]] - Wouter Meeussen (wouter.meeussen(AT)pandora.be), 
               Mar 24 2007
%o A052169 (Other) sage: from sage.combinat.sloane_functions import ExtremesOfPermanentsSequence2 
               sage: e = ExtremesOfPermanentsSequence2() sage: it = e.gen(1,2,1) 
               sage: [it.next() for i in range(20)] #(5 rows)# [From Zerinvary Lajos 
               (zerinvarylajos(AT)yahoo.com), May 15 2009]
%Y A052169 Pairwise sums of A002467.
%Y A052169 Sequence in context: A052324 A020115 A103816 this_sequence A020019 A020109 
               A020015
%Y A052169 Adjacent sequences: A052166 A052167 A052168 this_sequence A052170 A052171 
               A052172
%K A052169 nonn,easy
%O A052169 2,2
%A A052169 Aleksandar Petojevic (apetoje(AT)ptt.yu), Jan 26 2000
%E A052169 More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jan 31 2000