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Number of unconstrained walks on square lattice trapped after n steps.
11

%I #8 May 27 2024 11:25:52

%S 1,1,2,5,15,30,76,170,422,961,2339,5390,12977,30059,71918,167019,

%T 397691

%N Number of unconstrained walks on square lattice trapped after n steps.

%C See under A078527. In the probability sum in A077483 and A078526 the unconstrained walks are responsible for the occurrence of 3^(n-1) in the denominator of P(n).

%H Hugo Pfoertner, <a href="http://www.randomwalk.de/stw2d.html">Results for the 2D Self-Trapping Random Walk</a>

%e a(7)=1 because the unique shortest walk contains no constrained steps. a(10)=5: See illustration in "5 Unconstrained and 7 maximally 2-constrained walks of length 10" given at link.

%o (Fortran) c Program provided at given link

%Y Cf. A077482, A077483, A078526, A078527, A001411.

%K more,nonn

%O 7,3

%A _Hugo Pfoertner_, Nov 27 2002