A351888 Number of spanning trees of the graph acquired by placing a vertex in each of the n^2 cells of a triangle of size n in a triangular grid and placing edges between two vertices whenever two cells share a side.

1, 1, 6, 196, 33620, 29805312, 135418115000, 3137323702689792, 369428717972011445136, 220611233969267102720000000, 667057613878412272119535551460192, 10200716038735515318755655819186313101312, 788214513968528761154292411214871546938048625472

Offset

1,3

Comments

Conjecture: For each k there exists a sufficiently large N, such that for all n > N, if p_1, p_2, ..., p_k are the k largest primes that divide a(n) then (p_1*p_2*...*p_k)^2 also divides a(n).

Links

Peter Kagey, Table of n, a(n) for n = 1..50

Peter Kagey, One of the a(9) = 369428717972011445136 spanning trees on a triangle of size 9.

Crossrefs

Sequence in context: A241137 A086065 A200824 * A340557 A305167 A112845

Adjacent sequences: A351885 A351886 A351887 * A351889 A351890 A351891

Keyword

nonn

Author

Peter Kagey, Feb 23 2022

Status

approved