OFFSET
1,7
COMMENTS
The triangle T(n, k) is irregularly shaped: 0 <= k <= A093005(n), which means that A093005(n) is the maximal number of non-attacking ferses that can be placed on an n X n board. First row corresponds to n = 1. First column corresponds to k = 0.
Two placements that differ by rotation or reflection are counted only once.
A fers is a fairy chess piece attacking one step ne-nw-sw-se.
LINKS
Heinrich Ludwig, Table of n, a(n) for n = 1..130
Wikipedia, Fairy chess piece
EXAMPLE
Triangle begins:
1, 1;
1, 1, 1;
1, 3, 6, 7, 6, 2, 1;
1, 3, 17, 45, 92, 99, 76, 27, 7;
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Heinrich Ludwig, Nov 27 2016
STATUS
approved