OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..320
FORMULA
G.f.: (5*x-1)*(32*x^6+32*x^5-164*x^4-52*x^3+71*x^2-16*x+1) / ((x+1) *(192*x^7 +184*x^6 -1066*x^5 -113*x^4 +468*x^3 -166*x^2 +22*x-1)). - Alois P. Heinz, Jun 26 2012
MAPLE
b:= proc(n, i, j) option remember;
`if`(n<0 or i<0 or i>7 or j<0 or j>7, 0, `if`({n, i, j}={0},
1, add (add (b(n-1, i+t*r[1], j+t*r[2]), r=[[1, 1], [1, -1],
[-1, 1], [-1, -1]]), t=1..7)))
end:
a:= n-> b (n, 0, 0):
seq (a(n), n=0..30); # Alois P. Heinz, Jun 26 2012
MATHEMATICA
b[n_, i_, j_] := b[n, i, j] = If[n<0 || i<0 || i>7 || j<0 || j>7, 0, If[Union[{n, i, j}] == {0}, 1, Sum[Sum[b[n-1, i + t*r[[1]], j + t*r[[2]]], {r, {{1, 1}, {1, -1}, {-1, 1}, {-1, -1}}}], {t, 1, 7}]]]; a[n_] := b[n, 0, 0]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, May 28 2015, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved