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Search: id:A069996
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| A069996 |
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Number of spanning trees on the bipartite graph K_{3,n}. |
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+0
4
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| 1, 12, 81, 432, 2025, 8748, 35721, 139968, 531441, 1968300, 7144929, 25509168, 89813529, 312487308, 1076168025, 3673320192, 12440502369, 41841412812, 139858796529, 464904586800, 1537671920841, 5062810950252, 16600580533161
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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With a leading zero, this is the second binomial transform of the octagonal numbers A000567 and the binomial transform of A084857. - Paul Barry (pbarry(AT)wit.ie), Jun 09 2003
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FORMULA
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a(n) = n^2 * 3^(n-1)
E.g.f.: exp(3x)(x+3x^2) - Paul Barry (pbarry(AT)wit.ie), Jul 23 2003
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MATHEMATICA
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a[n_] := n^2*3^(n - 1); Table[ a[n], {n, 1, 24}]
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CROSSREFS
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Sequence in context: A012195 A147650 A007010 this_sequence A163020 A164300 A175037
Adjacent sequences: A069993 A069994 A069995 this_sequence A069997 A069998 A069999
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KEYWORD
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nonn
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AUTHOR
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Eric Weinhandl (eweinhandl(AT)msn.com), May 01 2002
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), May 04 2002
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