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Search: id:A152681
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| A152681 |
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[x^(n+1)]Reversion[x(1-x)/(1-3x)] |
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+0
2
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| 1, -2, 2, 2, -10, 6, 42, -102, -82, 782, -814, -3854, 12454, 5014, -98694, 142218, 472158, -1932258, -19038, 14816994, -27370410, -64159962, 334154442, -121279878, -2418497010, 5523511086, 8914677362, -61259567662, 44249714438
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Hankel transform is (-2)^C(n+1).
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FORMULA
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G.f.: (1+3x-sqrt(1+2x+9x^2))/(2x);
a(n)=sum{k=0..n, C(n+k,2k)*A000108(k)*(-3)^(n-k)};
a(n)=0^n-2*sum{k=0..floor((n-1)/2), C(n-1,2k)*A000108(k)(-1)^(n-k-1)*2^k};
a(n)=sum{k=0..n, A090181(n,k)*(-2)^k}. [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Feb 02 2009]
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CROSSREFS
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Cf. A125695.
Sequence in context: A155695 A091185 A125695 this_sequence A138674 A122946 A087628
Adjacent sequences: A152678 A152679 A152680 this_sequence A152682 A152683 A152684
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KEYWORD
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easy,sign
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Dec 10 2008
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