0,6

Among all the proof game problems counted in A090051, this is the number of problems ending in checkmate.

F. Labelle, Statistics on checkmate diagrams.

Retrograde Analysis Corner, Shortest Mates in Proof Games.

a(5)=3 because there are three checkmate proof games in 5 plies:

1. e4 e5 2. Qh5 Ke7 3. Qxe5#

1. e3 e5 2. Qh5 Ke7 3. Qxe5#

1. e4 f5 2. exf5 g5 3. Qh5#

Cf. A090051, A102784.

Sequence in context: A062216 A045489 A075869 this_sequence A105639 A003028 A069343

Adjacent sequences: A126682 A126683 A126684 this_sequence A126686 A126687 A126688

hard,nonn

Francois Labelle (flab(AT)cs.berkeley.edu), Feb 13 2007