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A131225
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Triangle read by rows: T(n,k) = 2*k - (1 + (-1)^(n-k))/2 (1 <= k <= n).
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2
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1, 2, 3, 1, 4, 5, 2, 3, 6, 7, 1, 4, 5, 8, 9, 2, 3, 6, 7, 10, 11, 1, 4, 5, 8, 9, 12, 13, 2, 3, 6, 7, 10, 11, 14, 15, 1, 4, 5, 8, 9, 12, 13, 16, 17, 2, 3, 6, 7, 10, 11, 14, 15, 18, 19, 1, 4, 5, 8, 9, 12, 13, 16, 17, 20, 21, 2, 3, 6, 7, 10, 11, 14, 15, 18, 19, 22, 23
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OFFSET
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1,2
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COMMENTS
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Row sums = A035608: (1, 5, 10, 18, 27, 39, ...).
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LINKS
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FORMULA
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EXAMPLE
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First few rows of the triangle:
1;
2, 3;
1, 4, 5;
2, 3, 6, 7;
1, 4, 5, 8, 9;
2, 3, 6, 7, 10, 11;
1, 4, 5, 8, 9, 12, 13;
...
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MAPLE
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T := proc (n, k) options operator, arrow; 2*k-1/2-(1/2)*(-1)^(n-k) end proc: for n to 10 do seq(T(n, k), k = 1 .. n) end do; # yields sequence in triangular form - Emeric Deutsch, Jul 09 2007
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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a(47), a(49) corrected and more terms from Georg Fischer, Jun 07 2023
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STATUS
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approved
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