OFFSET
1,2
FORMULA
a(n) = n^8 - A227479(n).
Conjecturally, a(p) = p^3(p^3-1)(p^2-1), for p prime. - Giovanni Resta, Jul 13 2013
MATHEMATICA
lon[n_]:=Length@matrices[n]; matrices[n_] := Flatten[Table[{{a, b}, {c, d}}, {a, n}, {b, n}, {c, n}, {d, n}], 3]; nocom[n_] := Sum[If[Mod[matrices[n][[i]].matrices[n][[j]] - matrices[n][[j]].matrices[n][[i]], n] == {{0, 0}, {0, 0}}, 0, 1], {i, lon[n]}, {j, i, lon[n]}]; Table[2*nocom[i], {i, 5}]
CROSSREFS
KEYWORD
nonn
AUTHOR
José María Grau Ribas, Jul 11 2013
EXTENSIONS
a(7)-a(25) from Giovanni Resta, Jul 13 2013
STATUS
approved