(n+5)(n+6)(n+7)(n+8)=
(n+5)(n+8) (n+6)(n+7)=
(n^2+13n+40)(n^2+13n+42)=
(A+40)(A+42)+1=
A^2+82A+1681=
(A+41)^2=
(n^2+13n+41)^2

5+8=6+7
と和が同じになれば良いのか