From elkies at math.harvard.edu Fri Jan 1 01:20:35 2021 From: elkies at math.harvard.edu (Elkies, Noam) Date: Fri, 1 Jan 2021 01:20:35 -0500 Subject: [Retros] Happy New Year Message-ID: It's that time of the year again: https://www.janko.at/Retros/d.php?ff=rnb1k1n1/pp1p1pp1/2p1p3/q3r2p/1Q1PP3/2B1b3/PPPNNPPP/2K1RB1R SPG-10.0; how many solutions? (C+; NDE 25.xii.2020) This time Andrew Buchanan took a different approach: see the last problem of https://chessbase.in/news/ChessBase-India-Christmas-New-Year-Solving-Contest-2020 and this year "Leon Xray" posted on Facebook a different kind of enumerative puzzle, with a nicely symmetrical diagram -- https://www.janko.at/Retros/d.php?ff=4k3/3ppp2/ppp3pp/8/8/PPP3PP/3PPP2/4K3 -- and a stipulation that makes it appropriate here, albeit barely: In how many ways can you add a White Queen and a Black Queen to this diagram to obtain a legal position? Wishing all a healthy and happy 2021, --Noam D. Elkies From keilhack at aol.com Tue Jan 19 01:30:52 2021 From: keilhack at aol.com (keilhack at aol.com) Date: Tue, 19 Jan 2021 06:30:52 +0000 (UTC) Subject: [Retros] Retro problems from the Stuttgarter Zeitung/solutions References: <1957975748.546503.1611037852927.ref@mail.yahoo.com> Message-ID: <1957975748.546503.1611037852927@mail.yahoo.com> 1) Werner Keym, shortest mate? (why?) Q7/ppk5/2P1P3/b1KpP3/8/2P5/8/8 w - - 0 1Solution: Not 1.e5:d6#?, as Kc8/d8:Bc7 Bb8-c7+ were possible last moves, but 1.Q:b7+ Kd8 2.Qd7#. 2) Werner Keym, shortest mate? (why?) 7R/6kp/4R1P1/4PpKp/7n/8/6P1/8 w - - 0 1 Solution: Not 1.e5:f6 e.p.+? K:h8 2.Re8#, as Kg8-g7 g7:h8R+ Kf8-g8 are possible last moves, so 1.R:h7+ Kf8 2.Rf7+ Kg8 3.Re8#. 3) Werner Keym/Bernd Schwarzkopf2k5/4K3/8/8/8/8/8/8 w - - 0 1Add 4 chessman. In the resulting position there shall be as much as possible ways to reach the same position after one white and one black move. Which is the position, and how many different moves by White are possible?Add wPg7 and black rooks on f8, g8, h8. g7:f8Q/R/B/K+ R:f8 and g7:h8Q/R/B/K R:h8, so eight different way to reach the same position! -------------- next part -------------- An HTML attachment was scrubbed... URL: