5,2
H. T. Croft, K. J. Falconer and R. K. Guy, Unsolved Problems in Geometry, B15.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Sequence in context: A141827 A143077 A203011 * A005828 A084764 A061789
Adjacent sequences: A005838 A005839 A005840 * A005842 A005843 A005844
nonn,hard,nice
N. J. A. Sloane (njas(AT)research.att.com).