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Search: id:A122896
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| A122896 |
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Riordan array for directed animals. |
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+0
4
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| 1, 0, 1, 0, 1, 1, 0, 2, 2, 1, 0, 4, 5, 3, 1, 0, 9, 12, 9, 4, 1, 0, 21, 30, 25, 14, 5, 1, 0, 51, 76, 69, 44, 20, 6, 1, 0, 127, 196, 189, 133, 70, 27, 7, 1, 0, 323, 512, 518, 392, 230, 104, 35, 8, 1, 0
(list; table; graph; listen)
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OFFSET
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0,8
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COMMENT
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Inverse of Riordan array (1, x/(1+x+x^2)). Product of A007318 and A122896 is A122897. Row sums are A005773, number of directed animals of size n.
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FORMULA
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Riordan array (1, (1-x-sqrt(1-2x-3x^2))/(2x)).
T(n+1,k+1)=A064189(n,k) . - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Apr 21 2007
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EXAMPLE
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Triangle begins
1,
0, 1,
0, 1, 1,
0, 2, 2, 1,
0, 4, 5, 3, 1,
0, 9, 12, 9, 4, 1,
0, 21, 30, 25, 14, 5, 1,
0, 51, 76, 69, 44, 20, 6, 1,
0, 127, 196, 189, 133, 70, 27, 7, 1,
0, 323, 512, 518, 392, 230, 104, 35, 8, 1,
0, 835, 1353, 1422, 1140, 726, 369, 147, 44, 9, 1
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CROSSREFS
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Sequence in context: A110124 A116389 A062110 this_sequence A107267 A112161 A128497
Adjacent sequences: A122893 A122894 A122895 this_sequence A122897 A122898 A122899
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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), Sep 18 2006
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