OFFSET
0,2
COMMENTS
Gives the number of possible chess games where both sides start without knights. Knights are still allowed to appear later in the game through promotion.
Does not include games which end in fewer than n plies.
The total number of such games should be less than the total number of standard chess games, and it appears A285875(n) <= A048987(n) for all n.
Initial terms computed using the Chesspresso engine.
EXAMPLE
a(1) = 18 because each pawn can move forward 1 or 2 squares (16 moves) and each rook can move into the square where the knight would have been (2 moves).
CROSSREFS
KEYWORD
nonn,hard,more,fini
AUTHOR
Sean A. Irvine, Apr 28 2017
STATUS
approved