|
|
A339074
|
|
Number of (undirected) cycles in the graph C_3 X C_n.
|
|
6
|
|
|
312, 1531, 7298, 35205, 174268, 885719, 4601982, 24306577, 129851384, 698930787, 3780126106, 20505863069, 111441343860, 606312668335, 3300926292470, 17978225967081, 97939845566896, 533619551723963, 2907629293865874, 15844069824657013, 86338863686763692, 470492593924667271
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
3,1
|
|
LINKS
|
|
|
PROG
|
(Python)
# Using graphillion
from graphillion import GraphSet
def make_CnXCk(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))
grids.append((i + (n - 1) * k, i))
for i in range(1, k * n, k):
for j in range(1, k):
grids.append((i + j - 1, i + j))
grids.append((i + k - 1, i))
return grids
universe = make_CnXCk(n, 3)
GraphSet.set_universe(universe)
cycles = GraphSet.cycles()
return cycles.len()
print([A339074(n) for n in range(3, 30)])
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|