OFFSET
1,2
COMMENTS
Power Group Enumeration applies here.
REFERENCES
E. Palmer and F. Harary, Graphical Enumeration, Academic Press, 1973.
LINKS
Marko Riedel et al., Unique rows of pebbles
FORMULA
With Z(S_{q,|m}) = [w^q] exp(Sum_{d|m} a_d w^d/d) and parameters n,k we have for nk even, (1/2) ((nk!)/k!/n!^k + (nk/2)! 2^(nk/2) [a_2^(nk/2)] Z(S_{k,|2})(Z_{n,|2}, a_2^n/n!) and for nk odd, (1/2) ((nk!)/k!/n!^k + ((nk-1)/2)! 2^((nk-1)/2) [a_1 a_2^((nk-1)/2)] Z(S_{k,|2})(Z_{n,|2}, a_2^n/n!). This sequence has k=4.
CROSSREFS
KEYWORD
nonn
AUTHOR
Marko Riedel, Dec 05 2017
STATUS
approved