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Search: id:A094639
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| 1, 2, 6, 31, 227, 1991, 19415, 203456, 2248356, 25887400, 307993016, 3763786812, 47032778956, 598933188956, 7751562502556, 101741582076581, 1351906409905481, 18159677984049581, 246298405721739581
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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A. F. Labossiere, Sobalian Coefficients.
A. F. Labossiere, Miscellaneous.
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FORMULA
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a(n) = Sum[ ((2k)!/(k!)^2/(k+1))^2, {k,0,n}. - Alexander Adamchuk, Feb 16 2008
Sum_{i=1..n} [c(i)]^2 = Sum_{i=1..n} [C(2*i-2, i-1)/i]^2 = (1/(n-1)!)^2 * [ n^C(2*n-4, 1) + {2*C(n-1, 2)}*n^(2*n-5) + {C(n-2, 0) + 4*C(n-2, 1) + 13*C(n-2, 2) + 22*C(n-2, 3) + 12*C(n-2, 4)}*n^C(2*n-6, 1) + {12*C(n-3, 1) + 152*C(n-3, 2) + 458*C(n-3, 3) + 640*C(n-3, 4) + 440*C(n-3, 5) + 120*C(n-3, 6)}*n^(2*n-7) + {40*C(n-4, 0) + 313*C(n-4, 1) + 2332*C(n-4, 2) + 9536*C(n-4, 3) + 21409*C(n-4, 4) + 28068*C(n-4, 5) + 21700*C(n-4, 6) + 9240*C(n-4, 7) + 1680*C(n-4, 8) + ... + C(n-3, 0)*((n-1)!)^2 ].
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CROSSREFS
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Cf. A000108, A094638, A014137, A001246, A033536, A000984, A006134, A082894, A002897, A079727.
Sequence in context: A058028 A054141 A007710 this_sequence A113719 A018225 A075845
Adjacent sequences: A094636 A094637 A094638 this_sequence A094640 A094641 A094642
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KEYWORD
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easy,nonn
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AUTHOR
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Andre F. Labossiere (boronali(AT)laposte.net), May 27 2004
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