Search: id:A002484
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%I A002484 M1524 N0597
%S A002484 1,2,5,20,87,616,4843,44128,444621,4936274,59661265,780547332,
%T A002484 10987097799,165587196328,2660378564791,45392026278108,819716784789209,
%U A002484 15620011000052754,313219935456572497,6593238656843759572
%N A002484 Number of menage permutations.
%D A002484 C. Berge, Principles of Combinatorics. Academic Press, NY, 1971, p. 162.
%D A002484 E. N. Gilbert, Knots and classes of menage permutations. Scripta Math. 
               22 (1956), 228-233 (1957).
%D A002484 J. Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 
               195.
%D A002484 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A002484 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%F A002484 Gilbert gives a formula (see Maple code).
%p A002484 with(numtheory): d := n->divisors(n): U := (m,t)->sum(2*m*binomial(2*m-k,
               k)*(m-k)!*(t-1)^k/(2*m-k),k=0..m): A := (n,i)->phi(n/dd[i])*(n/dd[i])^dd[i]*U(dd[i],
               1-dd[i]/n)/n: for n from 3 to 28 do dd := d(n): B := [seq(A(n,j),
               j=1..nops(dd))]: a[n] := sum(B[i],i=1..nops(B)) od: seq(a[n],n=3..28);
%Y A002484 Sequence in context: A008983 A012768 A006228 this_sequence A003069 A115082 
               A020105
%Y A002484 Adjacent sequences: A002481 A002482 A002483 this_sequence A002485 A002486 
               A002487
%K A002484 nonn,nice,easy
%O A002484 3,2
%A A002484 N. J. A. Sloane (njas(AT)research.att.com).
%E A002484 More terms and Maple code from Emeric Deutsch (deutsch(AT)duke.poly.edu), 
               Mar 08 2004

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