|
|
A368143
|
|
Number of ways of tiling the n X n torus up to 90-degree rotations of the square by two tiles that are each fixed under 90-degree rotation of the square.
|
|
3
|
|
|
2, 6, 28, 1171, 337664, 477339616, 2872202032640, 72057595967392816, 7462505059899322983424, 3169126500571074529242309120, 5492677668532710795071526353530880, 38716571525226776289479030777920527620096, 1106936151351216411420552029913564178922327982080
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
MATHEMATICA
|
A368143[n_] := 1/(4n^2)*(DivisorSum[n, Function[d, DivisorSum[n, Function[c, EulerPhi[c] EulerPhi[d] 2^(n^2/LCM[c, d])]]]] + n^2*If[OddQ[n], 2^((n^2 + 1)/2) + 2^((n^2 + 7)/4), 7*2^((n^2 - 4)/2) + 5*2^(n^2/4)])
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,changed
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|