[Retros] Maximum of Real e.p.+castle combinations is 192? Yefim 10/25/2004

[TregerYefim at aol.com]

      Hello from Yefim.
   Some other facts about En Passant.
1. As I said before, position
rnbqkbnr/8/8/pppppppp/PPPPPPPP/8/8/RNBQKBNR w KQkq - 0 1
may contain after "KQkq" 10 different e.p. squares, giving maximum of 
288 Fen strings (before last two digits). But those are Seeming e.p. 
relations.
2. How many Real e.p. relations (with castles) exist? Answer is: 192. 
   Position below illustrates this:
r3k2r/8/8/PppPppPp/pPPpPPpP/8/8/R3K2R w KQkq b6
where instead of b6 we may write c6; e6, f6, h6 and after changing
for "b" the following squares: b3,c3, e3, f3, h3.
  Taking into account 32 combinations with no e.p. squares and
 16*10=160 "e.p.+castle" combinations we got 32+160=192.
   Am I correct?

P.S. I suspect, for some reason somebody did not get my e-mail about
mutually exclusive castles, but it is in Retro archive (280367 positions 
leading
to the original One plus two "mirror" positions pointed out Francois). 


  
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