OFFSET
0,8
COMMENTS
Number of orbits under dihedral group D_6 of order 6. - N. J. A. Sloane, Sep 12 2019
LINKS
Heinrich Ludwig, Table of n, a(n) for n = 0..173
EXAMPLE
Triangle T(n, k) is irregularly shaped: 0 <= k <= n*(n+1)/2+1. The first row corresponds to n = 1, the first column corresponds to k = 0. Rows are palindromic.
1, 1;
1, 1, 1, 1;
1, 2, 4, 6, 4, 2, 1;
1, 3, 10, 25, 41, 48, 41, 25, 10, 3, 1;
...
There are T(3, 2) = 4 nonisomorphic choices of 2 points (X) in an equilateral triangle grid of side 3:
X . . X
. . X X . . X .
. X . . . . X . X . . .
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Heinrich Ludwig, Nov 14 2013
STATUS
approved