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Search: id:A158909
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| A158909 |
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Riordan array (1/((1-x)(1-x^2)),x/(1-x)^2). |
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+0
1
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| 1, 1, 1, 2, 3, 1, 2, 7, 5, 1, 3, 13, 16, 7, 1, 3, 22, 40, 29, 9, 1, 4, 34, 86, 91, 46, 11, 1, 4, 50, 166, 239, 174, 67, 13, 1, 5, 70, 296, 553, 541, 297, 92, 15, 1, 5, 95, 496, 1163, 1461, 1068, 468, 121, 17, 1
(list; table; graph; listen)
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OFFSET
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0,4
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COMMENT
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Row sums are F(n+1)F(n+2) or A001654(n+1). Diagonal sums are the Jacobsthal numbers A001045.
Transforms r^n into the symmetric third order sequence with g.f. 1/(1-(r+1)x-(r+1)x^2+x^3).
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FORMULA
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Number triangle T(n,k)=sum{i=0..n-k, (-1)^i C(n+k-i+1,2k-1)}.
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EXAMPLE
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Triangle begins
1,
1, 1,
2, 3, 1,
2, 7, 5, 1,
3, 13, 16, 7, 1,
3, 22, 40, 29, 9, 1,
4, 34, 86, 91, 46, 11, 1,
4, 50, 166, 239, 174, 67, 13, 1
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CROSSREFS
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Sequence in context: A109091 A138507 A109200 this_sequence A101477 A077887 A059379
Adjacent sequences: A158906 A158907 A158908 this_sequence A158910 A158911 A158912
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KEYWORD
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easy,nonn,tabl
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Mar 30 2009
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