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Search: id:A081918
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| A081918 |
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a(0) = 1; a(n) = n^(n-1)(3n-1)/2 (n>0) |
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+0
1
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| 1, 1, 5, 36, 352, 4375, 66096, 1176490, 24117248, 559607373, 14500000000, 414998793616, 13002646487040, 442663617327139, 16271152851709952, 642244372558593750, 27093655358260903936, 1216529796891671712025
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Main diagonal of square array T(n,k) where T(n,k)=k^n(n^2-n+2k^2)/(2k^2), in which rows have g.f. (1-2kx+(k^2+1)x^2)/(1-kx)^3.
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FORMULA
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a(0)=1, a(n)=a(n)=n^n(n^2-n+2n^2)/(2n^2), n>0.
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CROSSREFS
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Cf. A000124, A081908, A081909, A081910, A081911, A081912.
Sequence in context: A109186 A099391 A008785 this_sequence A062024 A031971 A132686
Adjacent sequences: A081915 A081916 A081917 this_sequence A081919 A081920 A081921
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Mar 31 2003
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