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A339622
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Number of Hamiltonian circuits within parallelograms of size 7 X n on the triangular lattice.
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2
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1, 498, 26499, 1475286, 100766213, 6523266332, 418172485806, 26971800950170, 1738936046774850, 112060168171247368, 7222422644817870197, 465494892350086836970, 30001329862709920944426, 1933604967243463575726934, 124622105764386987040047037, 8031972575008760516889720476
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OFFSET
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2,2
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LINKS
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PROG
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(Python)
# Using graphillion
from graphillion import GraphSet
def make_T_nk(n, k):
grids = []
for i in range(1, k + 1):
for j in range(1, n):
grids.append((i + (j - 1) * k, i + j * k))
if i < k:
grids.append((i + (j - 1) * k, i + j * k + 1))
for i in range(1, k * n, k):
for j in range(1, k):
grids.append((i + j - 1, i + j))
return grids
universe = make_T_nk(n, k)
GraphSet.set_universe(universe)
cycles = GraphSet.cycles(is_hamilton=True)
return cycles.len()
print([A339622(n) for n in range(2, 8)])
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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