This type of magic square is both a
regular magic square and a
multiplication magic square
at the same time. In 1955 Walter Horner discovered the first
addition-multiplication magic square of order 8 which has a magic constant
of 840 and a multiplication magic constant of 2058068231856000. In 2005
Christian Boyer found an addition-multiplication magic square with smaller
magic constants, which are 600 and 67463283888000.
