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Search: id:A108555
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| A108555 |
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Antidiagonal sums of square array A108553, in which row n equals the crystal ball sequence for D_n lattice. |
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+0
4
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| 1, 2, 5, 12, 35, 116, 411, 1482, 5333, 19030, 67265, 235704, 819863, 2834600, 9752951, 33428054, 114228713, 389419114, 1325155261, 4503031332, 15285291851, 51842203804, 175719341971, 595316455842, 2016131645245, 6826076021310
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Limit a(n+1)/a(n) ~ 3.3829757679..., real root of cubic (1+x+3*x^2-x^3).
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PROGRAM
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(PARI) {a(n)=if(n<0, 0, if(n==0, 1, sum(k=0, n, sum(j=0, k, binomial(n-j, k-j)* (binomial(2*(n-k), 2*j)-2*j*(n-k-j)*binomial(n-k, j)/if(n==k+1, 1, (n-k-1)))))))}
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CROSSREFS
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Cf. A108553, A108554.
Sequence in context: A000104 A000105 A055192 this_sequence A032203 A094717 A038142
Adjacent sequences: A108552 A108553 A108554 this_sequence A108556 A108557 A108558
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Jun 10 2005
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