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A065775
Array T read by diagonals: T(i,j)=least number of knight's moves on a chessboard (infinite in all directions) needed to move from (0,0) to (i,j).
17
0, 3, 3, 2, 2, 2, 3, 1, 1, 3, 2, 2, 4, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 2, 2, 2, 4, 4, 5, 3, 3, 3, 3, 3, 3, 5, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 3, 3, 3, 3, 5, 5, 5, 6, 6, 4, 4, 4, 4, 4, 4, 4, 6, 6, 7, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 7, 6, 6, 6, 6, 4, 4, 4, 4, 4, 6, 6, 6, 6, 7, 7, 7, 5, 5, 5, 5, 5, 5, 5, 5, 7, 7, 7
OFFSET
0,2
COMMENTS
For number of knight's moves to various subsets of the chessboard, see A018837, A183041 - A183053.
FORMULA
T(i,j) is given in cases:
Case 1: row 0
T(0,0)=0, T(1,0)=3, and for m>=1,
T(4m-2,0)=2m, T(4m-1,0)=2m+1, T(4m,0)=2m,
T(4m+1,0)=2m+1.
Case 2: row 1
T(0,1)=3, T(1,1)=2, and for m>=2,
T(4m-2,1)=2m-1, T(4m-1,1)=2m, T(4m,1)=2m+1,
T(4m+1,1)=2m+2.
Case 3: columns 1 and 2
(column 1) = (row 1); (column 2 = row 2).
Case 4: For i>=2 and j>=2,
T(i,j)=1+min{T(i-2,j-1),T(i-1,j-2)}.
Cases 1-4 determine T in the 1st quadrant;
all other T(i,j) are easily obtained by symmetry.
EXAMPLE
T(i,j) for -2<=i<=2 and -2<=j<=2:
4 1 2 1 4=T(2,2)
1 2 3 2 1=T(2,1)
2 3 0 3 2=T(2,0)
1 2 3 2 1=T(2,-1)
4 1 2 1 4=T(2,-2)
Corner of the array, T(i,j) for i>=0, k>=0:
0 3 2 3 2 3 4...
3 2 1 2 3 4 3...
2 1 4 3 2 3 4...
3 2 3 2 3 4 2...
CROSSREFS
Identical to A049604 except for T(1, 1).
Cf. A183041,...,A183042.
Sequence in context: A064983 A124933 A133884 * A096837 A139092 A366424
KEYWORD
nonn,tabl
AUTHOR
Stewart Gordon, Dec 05 2001
EXTENSIONS
Formula, examples, and comments by Clark Kimberling, Dec 20 2010
Example corrected by Clark Kimberling, Oct 14 2016
STATUS
approved