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A131225
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Triangle read by rows: T(n,k)=2k - [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, 4, 6, 8, 10, 11, 14, 15, 18, 19
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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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Table of n, a(n) for n=1..55.
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FORMULA
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2*A002260 - A128174, as infinite lower triangular matrices; where A002260 = (1; 1,2; 1,2,3;...) and A128174 = (1; 0,1; 1,0,1;...).
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EXAMPLE
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First few rows of the triangle are:
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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Cf. A002260, A128174, A035608.
Sequence in context: A094137 A038802 A092942 * A221919 A137671 A026370
Adjacent sequences: A131222 A131223 A131224 * A131226 A131227 A131228
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KEYWORD
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nonn,tabl
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AUTHOR
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Gary W. Adamson, Jun 20 2007
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STATUS
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approved
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