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%I #17 May 28 2021 19:11:21
%S 1,2,11,178,8590,1246850,550254085,741333619848,3046540983075504,
%T 38141694646516492843,1453908228148524205711098,
%U 168707605740228097581729005751,59588304533380500951726150179910606,64061403305026776755367065417308840021540
%N Number of self-avoiding walks of any length from NW to SW corners on an n X n grid or lattice.
%t A271465 = Cases[Import["https://oeis.org/A271465/b271465.txt", "Table"], {_, _}][[All, 2]];
%t a[n_] := A271465[[2 n^2 - 2 n + 1]];
%t Table[a[n], {n, 1, 14}] (* _Jean-François Alcover_, Sep 23 2019 *)
%o (Python)
%o # Using graphillion
%o from graphillion import GraphSet
%o import graphillion.tutorial as tl
%o def A271507(n):
%o if n == 1: return 1
%o universe = tl.grid(n - 1, n - 1)
%o GraphSet.set_universe(universe)
%o start, goal = 1, n
%o paths = GraphSet.paths(start, goal)
%o return paths.len()
%o print([A271507(n) for n in range(1, 10)]) # _Seiichi Manyama_, Mar 21 2020
%Y Main diagonal of A271465.
%Y Cf. A007764, A000532, A001184, A145157, A120443, A003763.
%K nonn
%O 1,2
%A _Andrew Howroyd_, Apr 08 2016
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