cp's OEIS Frontend

A333605 Number of directed Hamiltonian walks from NW to SW corners of a 9 X (2*n+1) grid.

%I A333605 #12 Mar 29 2020 01:24:22
%S A333605 1,128,28002,7503654,2087813834,585874869236,164719994049404,
%T A333605 46331085939142414,13032851914297031372,3666193548666012258524,
%U A333605 1031319586988812684556890,290115923359022569718438776,81611236566429170178900484740,22957699681804739055041075650848
%N A333605 Number of directed Hamiltonian walks from NW to SW corners of a 9 X (2*n+1) grid.
%H A333605 Seiichi Manyama, <a href="/A333605/b333605.txt">Table of n, a(n) for n = 0..200</a>
%o A333605 (Python)
%o A333605 # Using graphillion
%o A333605 from graphillion import GraphSet
%o A333605 import graphillion.tutorial as tl
%o A333605 def A271592(n, k):
%o A333605     if k == 1: return 1
%o A333605     universe = tl.grid(k - 1, n - 1)
%o A333605     GraphSet.set_universe(universe)
%o A333605     start, goal = 1, n
%o A333605     paths = GraphSet.paths(start, goal, is_hamilton=True)
%o A333605     return paths.len()
%o A333605 def A333605(n):
%o A333605     return A271592(9, 2 * n + 1)
%o A333605 print([A333605(n) for n in range(15)])
%Y A333605 Row n=9 of A271592 (with 0 omitted).
%Y A333605 Cf. A333584.
%K A333605 nonn
%O A333605 0,2
%A A333605 _Seiichi Manyama_, Mar 28 2020