|
%I #6 Mar 30 2012 16:49:37
%S 1,12,18,32,375,648,33614,196608,1594323,625000,14147686146,35831808,
%T 1792160394037,94911683664,1922167968750,140737488355328,
%U 8587269154529447379,61004779879896,10960773715569604371878,384000000000000000,123629392983875275287,978545447174632740656
%N Denominator of number J(n) arising in computation of second moment of A*_n lattice.
%D J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 476.
%e 0, 1/12, 5/18, 19/32, 389/375, 1045/648, 78077/33614, ...
%p J := proc(n) option remember; local i; if n <= 1 then 0 else (n!/(8*(n+1)*n^(n-2))) * add( n^k/k!, k=0..n) -n^2/(4*(n+1)) +(1/(n+1))*add( binomial(n,i)*(i/n)^i*( (n-i)/n)^(n-i-1)*J(i), i=1..n-1); fi; end;
%Y Cf. A072526.
%K nonn,frac
%O 1,2
%A _N. J. A. Sloane_, Aug 02 2003
|
