A007341 -id:A007341 - cp's OEIS frontend

A352022 Number of spanning trees in a hexagon of size n in the hexagonal grid.

1, 6, 176400, 95437674624600, 878617506040998925900403712, 134527385723138237635420920683683500322908000, 339161155484890894029987276076070590877762998258747782208794132480, 14004953513181662639884345044013838519837158205213642081126147144590500534440163767670000000

Offset: 0

Peter Kagey, Feb 28 2022

nonn

The hexagon of size n in the hexagonal grid has A033581(n) = 6*n^2 vertices.

Peter Kagey, Image of one of the a(3) = 95437674624600 spanning trees on a hexagon of size 3.

Cf. A007341 (square in square grid), A116469 (rectangle in square grid), A174579 (triangle in triangular grid), A351888 (triangle in hexagonal grid), A351994 (hexagon in triangular grid).

A338832 Number of spanning trees in the k_1 X ... X k_j grid graph, where (k_1 - 1, ..., k_j - 1) is the partition with Heinz number n.

Original entry on oeis.org

1, 1, 1, 4, 1, 15, 1, 384, 192, 56, 1, 31500, 1, 209, 2415, 42467328, 1, 49766400, 1, 2558976, 30305, 780, 1, 3500658000000, 100352, 2911, 8193540096000, 207746836, 1, 76752081000, 1, 20776019874734407680, 380160, 10864, 4140081, 242716067758080000000, 1

Offset: 1

Pontus von Brömssen, Nov 11 2020

nonn

a(n) > 1 precisely when n is composite.

			The partition (2, 2, 1) has Heinz number 18 and the 3 X 3 X 2 grid graph has a(18) = 49766400 spanning trees.

Pontus von Brömssen, Table of n, a(n) for n = 1..1151
Germain Kreweras, Complexité et circuits Eulériens dans les sommes tensorielles de graphes, J. Combin. Theory B 24 (1978), 202-212.
Eric Weisstein's World of Mathematics, Grid Graph
Eric Weisstein's World of Mathematics, Spanning Tree
Index entries for sequences related to trees

X n grid: A001353(n) = a(2*prime(n-1))
X n grid: A006238(n) = a(3*prime(n-1))
X n grid: A003696(n) = a(5*prime(n-1))
X n grid: A003779(n) = a(7*prime(n-1))
X n grid: A139400(n) = a(11*prime(n-1))
X n grid: A334002(n) = a(13*prime(n-1))
X n grid: A334003(n) = a(17*prime(n-1))
X n grid: A334004(n) = a(19*prime(n-1))
X n grid: A334005(n) = a(23*prime(n-1))
n X n grid: A007341(n) = a(prime(n-1)^2)
m X n grid: A116469(m,n) = a(prime(m-1)*prime(n-1))
X 2 X n grid: A003753(n) = a(4*prime(n-1))
X n X n grid: A067518(n) = a(2*prime(n-1)^2)
n X n X n grid: A071763(n) = a(prime(n-1)^3)
X ... X 2 grid: A006237(n) = a(2^n)

a(n) = Product_{n_1=0..k_1-1, ..., n_j=0..k_j-1; not all n_i=0} Sum_{i=1..j} (2*(1 - cos(n_i*Pi/k_i))) / Product_{i=1..j} k_i, where (k_1 - 1, ..., k_j - 1) is the partition with Heinz number n.

A340168 Decimal expansion of a constant related to the asymptotics of A004003.

Original entry on oeis.org

1, 1, 0, 8, 8, 6, 2, 2, 5, 8, 7, 8, 0, 7, 6, 7, 5, 1, 3, 2, 7, 6, 9, 5, 1, 1, 6, 2, 1, 3, 0, 8, 1, 9, 2, 9, 2, 6, 4, 5, 2, 6, 6, 1, 2, 6, 9, 6, 3, 5, 6, 9, 2, 2, 4, 3, 6, 2, 9, 4, 3, 1, 4, 1, 8, 4, 4, 7, 3, 5, 5, 6, 5, 3, 0, 9, 3, 4, 8, 6, 6, 3, 2, 1, 3, 4, 3, 9, 7, 1, 4, 6, 7, 5, 0, 7, 9, 0, 1, 5, 5, 7, 4, 0, 5

Offset: 1

Vaclav Kotesovec, Dec 30 2020

			1.1088622587807675132769511621308192926452661269635692243629431418447355653...

Cf. A004003, A007341, A007726, A065072, A127605, A340052.

RealDigits[2*E^(Catalan/Pi)/(1 + Sqrt[2]), 10, 110][[1]]

Equals lim_{n->infinity} A004003(n) / ((sqrt(2)-1)^(2*n) * exp(4*G*n*(n+1)/Pi)), where G is the Catalan's constant A006752.

Equals 2*exp(G/Pi) / (1 + sqrt(2)), where G is Catalan's constant A006752.

cp's OEIS Frontend

A352022 Number of spanning trees in a hexagon of size n in the hexagonal grid.

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A338832 Number of spanning trees in the k_1 X ... X k_j grid graph, where (k_1 - 1, ..., k_j - 1) is the partition with Heinz number n.

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A340168 Decimal expansion of a constant related to the asymptotics of A004003.

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