A350191 Number of ways of placing maximum number of nonattacking rooks on a triangular board with edge-length n (not counting rotations and reflections as distinct).

1, 1, 1, 1, 5, 3, 1, 45, 29, 5, 807, 422, 29, 20022, 8270, 224, 642162, 211848, 3012

Offset

1,5

Comments

a(n) = A350041(n) for n <> 10,13,16,19,...

Conjecture: a(3*n-2) = A309260(n). There is a nice analogy with A289893(3*n+1) = A002047(n).

Links

Table of n, a(n) for n=1..19.

Alain Brobecker, Non Attacking Rooks on Hexhex and Triangular boards

Vaclav Kotesovec, Example: All non-identical positions for n = 10, a(10) = 5

Crossrefs

Cf. A350041, A289893.

Sequence in context: A352136 A143410 A114344 * A350041 A317674 A201333

Adjacent sequences: A350188 A350189 A350190 * A350192 A350193 A350194

Keyword

nonn,more,hard

Author

Vaclav Kotesovec, Dec 19 2021

Status

approved