OFFSET
0,2
COMMENTS
An orientation of the edges of the d-dimensional hypercube is recursively combed if there is at least one dimension along which all the edges go into the same direction and the two (d-1)-dimensional cube orientations resulting from the removal of all edges along that dimension are again recursively combed.
REFERENCES
GWOP 2008, 6th Gremo Workshop on Open Problems
FORMULA
f(n) = sum((-1)^(j+1)*2^j*binomial(n,j)*f(n-j)^(2^j), j=1..n), f(0) = 1
MAPLE
f[0] := 1; for k from 1 to 8 do f[k] := sum((-1)^(j+1)*2^j*binomial(k, j)*f[k-j]^(2^j), j=1..k); od;
CROSSREFS
KEYWORD
nonn
AUTHOR
Philipp Zumstein (zuphilip(AT)inf.ethz.ch), Sep 16 2008
STATUS
approved