5) (n, k) are positive integers, solve n(n + 2) = k^2
6) (n, k) are positive integers, solve n(n + 4) = k^2
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{n,k}⊂Z
n(n+2)=k2
k∈{ 4, 9, 16, 25, 36, 49, 64, 81, 100, 121 }
n∈{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}
n(n+2)∈{3, 8, 15, 24, 35, 48, 63, 80, 99, 120, 143, 168}
No solution for positive n, but if n = -1
−1(−1+2)=i2
n(n+5)=k2
No solution for positive n, but if n = -4
−4(−4+5)=(2i)2
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