A223234 Rolling icosahedron footprints: number of 2 X n 0..11 arrays starting with 0 where 0..11 label vertices of an icosahedron and every array movement to a horizontal, diagonal or antidiagonal neighbor moves along an icosahedral edge.
12, 65, 785, 7445, 75665, 753005, 7540985, 75377045, 753868865, 7538393405, 75384819785, 753845540645, 7538463378065, 75384609865805, 753846170402585, 7538461488792245, 75384615533623265, 753846153399130205
Offset: 1
Keywords
Examples
Some solutions for n=3: ..0..2..1....0..7.11....0..6..2....0..6..5....0..7..3....0..2..1....0..2..0 ..0..7..0....3..7..3...10..6..4....4..6..5....3..7..0....6..2..8....8..2..4 Vertex neighbors: 0 -> 1 2 5 6 7 1 -> 0 2 3 7 8 2 -> 0 1 4 6 8 3 -> 1 7 8 9 11 4 -> 2 6 8 9 10 5 -> 0 6 7 10 11 6 -> 0 2 4 5 10 7 -> 0 1 3 5 11 8 -> 1 2 3 4 9 9 -> 3 4 8 10 11 10 -> 4 5 6 9 11 11 -> 3 5 7 9 10
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Cf. A223233.
Formula
Empirical: a(n) = 7*a(n-1) + 30*a(n-2) for n>3.
Conjectures from Colin Barker, Aug 17 2018: (Start)
G.f.: x*(12 - 19*x - 30*x^2) / ((1 + 3*x)*(1 - 10*x)).
a(n) = (-25*(-1)^n*3^(1+n) + 49*10^n) / 65 for n>1.
(End)
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