A series is given with one term missing. Choose the correct alternatives from the given ones that will complete the series. 806, 975, ?, 935, 886, 911, 902

The series alternates between two patterns starting from different positions: From 806: 806 + 53 = 859, 859 - ? = 935 (doesn't fit). Looking differently: 806→886→902→? (subtract 18, add 16, pattern unclear). 975→935→911 (subtract 40, subtract 24). Let's try: 806→886 (-80), 886→902 (+16), 902→911 (+9)... Not clear. Alternative: 806→975→?→935→886→911→902. Going from right: 975+? = ?+? = 935+886 = 1821... This is complex. The pattern appears to be: 806→975 (+169), 975→854 (-121), 854→935 (+81), 935→886 (-49), 886→911 (+25), 911→902 (-9). The differences are squares of odd numbers in reverse: 13², 11², 9², 7², 5², 3². So ? = 854.