%I #27 Oct 28 2021 20:24:51

%S 1,12,99,700,4569,28476,172508,1026288,6033690,35195512,204232809,

%T 1181052756,6814746393,39267916380,226097749224,1301403695520,

%U 7490649175326,43123589230824,248351880642630,1430956006648056,8249467230853002,47587180659332248

%N Number of walks of length n on the simple cubic lattice terminating at height 2 above the (x,y)-plane.

%H Rigoberto Flórez, Leandro Junes, and José L. Ramírez, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL21/Florez/florez4.html">Further Results on Paths in an n-Dimensional Cubic Lattice</a>, Journal of Integer Sequences, Vol. 21 (2018), Article 18.1.2.

%H R. K. Guy, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL3/GUY/catwalks.html">Catwalks, sandsteps and Pascal pyramids</a>, J. Integer Sequences, Vol. 3 (2000), Article #00.1.6.

%p b:= proc(n, k) option remember; `if`(min(n, k)<0, 0,

%p `if`(max(n, k)=0, 1, b(n-1, k-1)+4*b(n-1, k)+b(n-1, k+1)))

%p end:

%p a:= n-> b(n, 2):

%p seq(a(n), n=2..25); # _Alois P. Heinz_, Oct 28 2021

%Y Column 2 of A052179.

%K nonn,walk

%O 2,2

%A _N. J. A. Sloane_, Jan 26 2000

%E More terms and title improved by _Sean A. Irvine_, Oct 28 2021