OFFSET
0,5
REFERENCES
J. O'Rourke, Art Gallery Theorems and Algorithms, Oxford Univ. Press, 1987, p. 222.
MATHEMATICA
Table[Sum[Min[k, n-k]EulerPhi[k](n-k), {k, 2, n}], {n, 0, 50}] (* Harvey P. Dale, May 02 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Feb 17 2004
STATUS
approved