theorem Th87: :: NEWTON02:185

for a being Nat holds
( not 7 divides (a |^ 3) - 2 & not 7 divides (a |^ 3) + 2 & not 7 divides (a |^ 3) - 3 & not 7 divides (a |^ 3) + 3 & not 7 divides (a |^ 3) - 4 & not 7 divides (a |^ 3) + 4 & not 7 divides (a |^ 3) - 5 & not 7 divides (a |^ 3) + 5 )