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A026681
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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-1,k) if k or n-k is of form 2h for h=1,2,...,[ n/4 ], else T(n,k)=T(n-1,k-1)+T(n-2,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, 7, 10, 7, 1, 1, 9, 17, 17, 9, 1, 1, 11, 26, 44, 26, 11, 1, 1, 13, 37, 87, 87, 37, 13, 1, 1, 15, 50, 150, 174, 150, 50, 15, 1, 1, 17, 65, 237, 324, 324, 237, 65, 17, 1, 1, 19, 82, 352, 561, 822, 561, 352, 82, 19, 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) for i even and j >= i and for j even and i >= j.
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CROSSREFS
| Sequence in context: A130154 A134398 A026615 * A109128 A113245 A103450
Adjacent sequences: A026678 A026679 A026680 * A026682 A026683 A026684
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KEYWORD
| nonn,tabl
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AUTHOR
| Clark Kimberling (ck6(AT)evansville.edu)
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