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1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 12, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Row sums = A032766, congruent to {0,1} mod 3: (1, 3, 4, 6, 7, 9, 10,...).
Sequence array for the expansion of (1+2x)/(1-x^2). A105476 is an eigensequence. [From Paul Barry (pbarry(AT)wit.ie), Nov 03 2010]
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FORMULA
| 3*A128174 - 2*A000012(signed + - + 1 by columns). (1, 2, 1, 2, 1,...) in every column.
Triangle T(n,k)=if(k<=n,(3-(-1)^(n-k))/2). [From Paul Barry (pbarry(AT)wit.ie), Nov 03 2010]
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EXAMPLE
| First few rows of the triangle are:
1;
2, 1;
1, 2, 1;
2, 1, 2, 1;
1, 2, 1, 2, 1;
2, 1, 2, 1, 2, 1;
...
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CROSSREFS
| Cf. A128174, A000012, A032766.
Sequence in context: A175077 A001030 A071709 * A029440 A061337 A103684
Adjacent sequences: A131403 A131404 A131405 * A131407 A131408 A131409
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KEYWORD
| nonn,tabl
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AUTHOR
| Gary W. Adamson (qntmpkt(AT)yahoo.com), Jul 07 2007
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