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%I #132 Apr 07 2020 11:03:06
%S 1,4,47,1843,232905,92729439,115234959344,442748883422394
%N Number of self-avoiding closed paths on an n X n grid which pass through NW and SW corners.
%C a(11) = 188829168009674568016545. - _Seiichi Manyama_, Apr 07 2020
%e a(2) = 1;
%e +--*
%e | |
%e +--*
%e a(3) = 4;
%e +--*--* +--*--* +--* +--*
%e | | | | | | | |
%e * * * *--* * *--* * *
%e | | | | | | | |
%e +--*--* +--* +--*--* +--*
%o (Python)
%o # Using graphillion
%o from graphillion import GraphSet
%o import graphillion.tutorial as tl
%o def A333247(n):
%o universe = tl.grid(n - 1, n - 1)
%o GraphSet.set_universe(universe)
%o cycles = GraphSet.cycles().including(1).including(n)
%o return cycles.len()
%o print([A333247(n) for n in range(2, 10)])
%Y Cf. A271507, A333246, A333323, A333466.
%K nonn,more
%O 2,2
%A _Seiichi Manyama_, Mar 23 2020
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