⊦ 0 < i → Π all_prime_divisors(i) = i
0 < j → Π all_prime_divisors(j) = j, 0 ≤ j ⊦ ∃ i, i0, i1, i2. j = i ^2 + i0 ^2 + i1 ^2 + i2 ^2
Used terms: j