n*(n+1)*(n+2)*(n+3) + 1 = [n*(n+3) + 1]^2 = [(n+1)*(n+2) - 1]^2
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(n^2 + n)*(n^2 + 5*n + 6) +1 =
= n^4 + 5*n^3 + 6*n^2 + n^3 + 5*n^2 + 6*n + 1 =
= n^4 + 6*n^3 + 11*n^2 + 6*n + 1
(n^2 + 3*n + 1) * (n^2 + 3*n + 1) =
= n^4 + 3*n^3 + n^2 + 3*n^3 + 9*n^2 + 3*n + n^2
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