let k, i, j be Element of NAT ; for f being FinSequence of (TOP-REAL 2)
for G being Go-board st 1 <= k & k + 1 <= len f & f is_sequence_on G & [i,(j + 1)] in Indices G & [i,j] in Indices G & f /. k = G * i,(j + 1) & f /. (k + 1) = G * i,j holds
front_right_cell f,k,G = cell G,(i -' 1),(j -' 1)
let f be FinSequence of (TOP-REAL 2); for G being Go-board st 1 <= k & k + 1 <= len f & f is_sequence_on G & [i,(j + 1)] in Indices G & [i,j] in Indices G & f /. k = G * i,(j + 1) & f /. (k + 1) = G * i,j holds
front_right_cell f,k,G = cell G,(i -' 1),(j -' 1)
let G be Go-board; ( 1 <= k & k + 1 <= len f & f is_sequence_on G & [i,(j + 1)] in Indices G & [i,j] in Indices G & f /. k = G * i,(j + 1) & f /. (k + 1) = G * i,j implies front_right_cell f,k,G = cell G,(i -' 1),(j -' 1) )
A1:
( j < j + 1 & j + 1 <= (j + 1) + 1 )
by XREAL_1:31;
assume
( 1 <= k & k + 1 <= len f & f is_sequence_on G & [i,(j + 1)] in Indices G & [i,j] in Indices G & f /. k = G * i,(j + 1) & f /. (k + 1) = G * i,j )
; front_right_cell f,k,G = cell G,(i -' 1),(j -' 1)
hence
front_right_cell f,k,G = cell G,(i -' 1),(j -' 1)
by A1, Def4; verum