2.10.108 Number Series

Condition: using a sign of koshi, investigate a series for convergence: \ [\ sum_ {n = 1}^{\ infty} \ left (-\ frac {2} {-5 n-1} \ right)^{-\ frac {7 n^{3}+n^{2} +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 +7 n+4} {6}} \]