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A291904
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Triangle read by rows: T(n,k) = T(n-k,k-1) + T(n-k,k+1) with T(0,0) = 1 for 0 <= k <= A003056(n).
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5
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1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 0, 0, 2, 1, 0, 0, 2, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 3, 2, 0, 0, 3, 2, 1, 1, 1, 0, 2, 3, 2, 1, 0, 0, 3, 4, 3, 1, 0, 0, 4, 4, 3, 2, 1, 0, 4, 6, 4, 2, 0, 0, 6, 7
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OFFSET
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0,38
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COMMENTS
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T(n,k) is the number of integer compositions of n with first part 1, last part k, and all adjacent differences in {-1,1}. - John Tyler Rascoe, Aug 14 2023
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LINKS
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FORMULA
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This triangle is T_1(n,k) of the general triangle T_m(n,k) for compositions of this kind with first part m.
T_m(0,0) = T_m(m,m) = 1.
T_m(n,k) = T_m(n-k,k-1) + T_m(n-k,k+1) for m < n and 0 < k <= A003056(n+A000217(m-1)).
T_m(n,k) = 0 for 0 < n < m or n < k.
T_m(n,0) = 0 for 0 < n. (End)
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EXAMPLE
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First few rows are:
1;
0, 1;
0, 0;
0, 0, 1;
0, 1, 0;
0, 0, 0;
0, 0, 1, 1;
0, 1, 0, 0;
0, 0, 1, 0;
0, 1, 1, 1;
0, 1, 0, 0, 1;
0, 0, 2, 1, 0;
0, 2, 1, 1, 0.
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MATHEMATICA
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T[0, 0] = 1; T[_, 0] = 0; T[n_?Positive, k_] /; 0 < k <= Floor[(Sqrt[8n+1] - 1)/2] := T[n, k] = T[n-k, k-1] + T[n-k, k+1]; T[_, _] = 0;
Table[T[n, k], {n, 0, 20}, {k, 0, Floor[(Sqrt[8n+1] - 1)/2]}] // Flatten (* Jean-François Alcover, May 29 2019 *)
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CROSSREFS
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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