A079479 Denominator of number J(n) arising in computation of second moment of A*_n lattice.

1, 12, 18, 32, 375, 648, 33614, 196608, 1594323, 625000, 14147686146, 35831808, 1792160394037, 94911683664, 1922167968750, 140737488355328, 8587269154529447379, 61004779879896, 10960773715569604371878, 384000000000000000, 123629392983875275287, 978545447174632740656

Offset

1,2

References

J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 476.

Links

Table of n, a(n) for n=1..22.

Example

0, 1/12, 5/18, 19/32, 389/375, 1045/648, 78077/33614, ...

Maple

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;

Crossrefs

Cf. A072526.

Sequence in context: A007371 A277725 A319746 * A293692 A349027 A348965

Adjacent sequences: A079476 A079477 A079478 * A079480 A079481 A079482

Keyword

nonn,frac

Author

N. J. A. Sloane, Aug 02 2003

Status

approved