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Search: id:A095922
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| A095922 |
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Dimension of invariants of n-th tensor power of 5-dimensional irreducible representation of B_2. |
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+0
2
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| 1, 0, 1, 0, 3, 1, 15, 15, 105, 190, 945, 2410, 10263, 31890, 127699, 444458, 1751685, 6518736, 25807445, 100152288, 401449271, 1602902055, 6519160851, 26580508625, 109656966853, 454524861846, 1899821492925, 7982263725826, 33757439931675
(list; graph; listen)
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OFFSET
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0,5
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COMMENT
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The analogous sequence for G_2 is A059710.
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REFERENCES
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Alec Mihailovs, A Combinatorial Approach to Representations of Lie Groups and Algebras, Springer-Verlag New York (2004).
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FORMULA
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a(n) =sum(A000108(i)*A000108(i+1)*binomial(n, 2*i), i=0..floor(n/2)) - sum(A000108(i)^2*binomial(n, 2*i-1), i=0..floor((n+1)/2)); exponential generating function = exp(t)*b(t) where b(t) is the exponential generating function of the sequence B(n) = (-1)^n*A000108(floor((n+1)/2))*A000108(floor(n/2+1)).
a(0)=1, a(1)=0, a(2)=1 and (n+3)(n+4)a(n)=3(n-1)(n+2)a(n-1)+(n-1)(13n+4)a(n-2)-15(n-1)(n-2)a(n-3) for n>2.
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EXAMPLE
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a(2)=1 because SO(5) has unique (up to multiplication by a constant) invariant in V\otimes V - the quadratic form x^2+y^2+z^2+u^2+v^2.
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MAPLE
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ca:=n->binomial(n+n, n)/(n+1); a:=n->add(ca(i)*ca(i+1)*binomial(n, 2*i), i=0..floor(n/2))- add(ca(i)^2*binomial(n, 2*i-1), i=0..floor((n+1)/2)); seq(a(n), n=0..40);
A095922:=rsolve({(n+3)*(n+4)*A(n)=3*(n-1)*(n+2)*A(n-1)+(n-1)*(13*n+4)*A(n-2)-15*\ (n-1)*(n-2)*A(n-3), A(0)=1, A(1)=0, A(2)=1}, A(n), makeproc);
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CROSSREFS
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Cf. A000108, A059710.
Sequence in context: A144006 A113378 A156289 this_sequence A089278 A087071 A053485
Adjacent sequences: A095919 A095920 A095921 this_sequence A095923 A095924 A095925
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KEYWORD
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easy,nice,nonn
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AUTHOR
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Alec Mihailovs (alec(AT)mihailovs.com), Jul 11 2004
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