OFFSET
1,5
COMMENTS
The second column is A113947.
REFERENCES
J. H. Kwak, A. Mednykh and V. Liskovets, Enumeration of branched coverings of nonorientable surfaces with cyclic branch points, SIAM J. Discrete Math., Vol. 19, No. 2 (2005), 388-398.
FORMULA
E.g. for n=7 and r>=1, a(7, r)=(2*720^(r-1)+(-1)^r*2*120^(r-1)+2*48^(r-1)+(-1)^r*36^(r-1)+6^r)/7 (more generally, a(7, r, h)=7^(h-2)*(2*720^m+(-1)^r*2*120^m+2*48^m+(-1)^r*36^m+6^r) for 7-sheeted coverings of the non-orientable surface of genus h>=1, where m=h+r-2).
EXAMPLE
The array begins:
1 1 1 1 1 1 1 ...
0 2 0 2 0 2 0 ...
1 3 5 11 21 43 85 ...
0 8 0 128 0 3968 0 ...
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Valery A. Liskovets, Nov 10 2005
STATUS
approved