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Search: id:A108554
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| A108554 |
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Main diagonal 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, 3, 13, 147, 1681, 18733, 204205, 2195399, 23429185, 249258777, 2650436845, 28209301211, 300745906449, 3212758605189, 34392151363021, 368908132170511, 3964622452867329, 42682164804034609, 460242445806795853
(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) ~ 11.08...
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PROGRAM
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(PARI) {a(n)=if(n<0, 0, if(n==0, 1, if(n==1, 3, sum(j=0, n, binomial(2*n-j, n-j)* (binomial(2*n, 2*j)-2*j*(n-j)*binomial(n, j)/(n-1))))))}
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CROSSREFS
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Cf. A108553, A108555.
Sequence in context: A130589 A041591 A001150 this_sequence A014376 A065622 A140421
Adjacent sequences: A108551 A108552 A108553 this_sequence A108555 A108556 A108557
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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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