OFFSET
1,2
EXAMPLE
a(2)=6 because the determinants of the 24 2 X 2 matrices whose entries are all permutations of 1,2,3,4 can only assume the values -10,-5,-2,2,5,10.
MATHEMATICA
f[n_] := (p = Permutations[ Table[i, {i, n^2}]]; Length[ Union[ Table[ Det[ Partition[ p[[i]], n]], {i, 1, (n^2)!}]]]) (* Robert G. Wilson v *)
PROG
See link given in A088238.
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Hugo Pfoertner, Sep 23 2003
EXTENSIONS
Minor edits and a(6) from Hugo Pfoertner, Sep 08 2019
STATUS
approved