OFFSET
1,5
COMMENTS
It is known that a(10)=0.
Walter Trump estimates a(8) ~= 4.677*10^15 and a(9) ~= 1.363*10^24.
REFERENCES
Gardner, M. "Magic Squares and Cubes." Ch. 17 in Time Travel and Other Mathematical Bewilderments. New York: W.H. Freeman, pp. 213-225, 1988.
LINKS
Eric Weisstein's World of Mathematics, Associative Magic Square
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Eric W. Weisstein, Mar 14 2003
EXTENSIONS
a(6)-a(7) from Walter Trump's website, added by Max Alekseyev, May 22 2008
STATUS
approved