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A026703
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Triangular array T read by rows: T(n,0)=T(n,n)=1 for n >= 0; for n >= 2 and 1<=k<=n-1, T(n,k)=T(n-1,k-1)+T(n-2,k-1)+T(n-1,k) if k=[ n/2 ] or k=[ (n+1)/2 ], else T(n,k)=T(n-1,k-1)+T(n-1,k).
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15
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1, 1, 1, 1, 3, 1, 1, 5, 5, 1, 1, 6, 13, 6, 1, 1, 7, 24, 24, 7, 1, 1, 8, 31, 61, 31, 8, 1, 1, 9, 39, 116, 116, 39, 9, 1, 1, 10, 48, 155, 293, 155, 48, 10, 1, 1, 11, 58, 203, 564, 564, 203, 58, 11, 1, 1, 12, 69, 261, 767, 1421, 767, 261, 69, 12, 1
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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FORMULA
| T(n, k) = number of paths from (0, 0) to (n-k, k) in the directed graph having vertices (i, j) and edges (i, j)-to-(i+1, j) and (i, j)-to-(i, j+1) for i, j >= 0 and edges (i, j)-to-(i+1, j+1) if |i-j|<=1.
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CROSSREFS
| Sequence in context: A191751 A131767 A026780 * A122917 A096583 A130154
Adjacent sequences: A026700 A026701 A026702 * A026704 A026705 A026706
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KEYWORD
| nonn,tabl
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AUTHOR
| Clark Kimberling (ck6(AT)evansville.edu)
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