theorem Th35: :: NUMBER02:35

for n being Nat holds
( not 7 divides n iff ex k being Nat st
( n = (7 * k) + 1 or n = (7 * k) + 2 or n = (7 * k) + 3 or n = (7 * k) + 4 or n = (7 * k) + 5 or n = (7 * k) + 6 ) )