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Search: id:A133708
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| 0, 0, 1, 69, 1694, 22932, 208152, 1413720, 7697052, 35194302, 139687119, 493127635, 1577331756, 4637757488, 12679063488, 32529562560, 78917794128, 182184724908, 402332471541, 853769650041, 1747606106554, 3462012537060
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OFFSET
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1,4
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FORMULA
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In terms of Vandermonde determinants, a(n) = 1/864*sum {1 <= x_1,x_2,x_3 <= n} (x_1*x_2*x_3)^2*(det V(x_1,x_2,x_3))^2 = 1/864 *sum {1 <= i,j,k <= n} (i*j*k*(i-j)(i-k)(j-k))^2, where V(x_1,x_2,x_3) is the Vandermonde matrix of order 3. a(n) = (n-2)*(n-1)^2*n^3*(n+1)^3*(n+2)^2*(n+3)*(n^2+n+3)*(2n+1)/108864000.
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CROSSREFS
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Cf. A040977, A047819, A047835, A107915.
Adjacent sequences: A133705 A133706 A133707 this_sequence A133709 A133710 A133711
Sequence in context: A093269 A108147 A095255 this_sequence A017785 A017732 A114028
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KEYWORD
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nonn
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AUTHOR
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Peter Bala (pbala(AT)toucansurf.com), Sep 21 2007
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