%I A028447
%S A028447 3,32,229,1845,14320,112485,880163,6895792,54003765,422983905,
%T A028447 3312866080,25947198337,203223953179,1591695681488,12466511517581,
%U A028447 97640484615909,764741896529104,5989627994067061,46912093390144139
%N A028447 Number of perfect matchings in graph P_{2} X P_{3} X P_{n}.
%C A028447 lim(a(n)^(1/n), n -> infinity) = 7.832221... - Emeric Deutsch (deutsch(AT)duke.poly.edu), 
               Oct 14 2006
%D A028447 Per Hakan Lundow, "Computation of matching polynomials and the number 
               of 1-factors in polygraphs", Research report, No 12, 1996, Department 
               of Math., Umea University, Sweden.
%D A028447 H. Narumi and H. Hosoya, Generalized expression of the perfect matching 
               number of 2 X 3 X n lattices, J. Math. Phys. 34 (3), 1993, 1043-1051.
%H A028447 Per Hakan Lundow, <a href="http://www.theophys.kth.se/~phl/Text/1factors2.ps.gz">
               Enumeration of matchings in polygraphs</a>, 1998.
%F A028447 a(n) = 6a(n - 1) + 21a(n - 2) - 42a(n - 3) - 89a(n - 4) + 68a(n - 5) 
               + 89a(n - 6) - 42a(n - 7) - 21a(n - 8) + 6a(n - 9) + a(n - 10). - 
               Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 14 2006
%p A028447 a[0]:=1: a[1]:=3: a[2]:=32: a[3]:=229: a[4]:=1845: a[5]:=14320: a[6]:=112485: 
               a[7]:=880163: a[8]:=6895792: a[9]:=54003765: a[10]:=422983905: for 
               n from 11 to 20 do a[n]:=6*a[n-1]+21*a[n-2]-42*a[n-3]-89*a[n-4]+68*a[n-5]+89*a[n-6]-42*a[n-7]-21*a[n-8]+6\
               *a[n-9]+a[n-10] od: seq(a[n],n=1..19); - Emeric Deutsch (deutsch(AT)duke.poly.edu), 
               Oct 14 2006
%Y A028447 Sequence in context: A119940 A004256 A002059 this_sequence A081012 A035533 
               A029502
%Y A028447 Adjacent sequences: A028444 A028445 A028446 this_sequence A028448 A028449 
               A028450
%K A028447 nonn
%O A028447 1,1
%A A028447 Per Hakan Lundow (phl(AT)theophys.kth.se)