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

TregerYefim at aol.com TregerYefim at aol.com
Fri Oct 15 09:29:56 EDT 2004

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.
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
to the original One plus two "mirror" positions pointed out Francois).

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