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Search: id:A127897
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| A127897 |
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Series reversion of x/(1+2x+3x^2+x^3). |
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+0
2
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| 0, 1, 2, 7, 27, 114, 507, 2342, 11125, 54002, 266684, 1335610, 6767477, 34629709, 178701317, 928903447, 4859345882, 25563551782, 135153617840, 717740916202, 3826894116962, 20478451476328, 109945087353190
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Series reversion of A127896.
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FORMULA
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G.f.: 2*sqrt(3)*sqrt((1+x)/x)*sin(asin(3*sqrt(3)/(2*sqrt((1+x)/x)))/3)/3; a(n)=sum{k=0..n-1, sum{j=0..k, (1/(2k+j-1))*C(n-1,3k-j)*C(3k-j,k)*C(k,j)*2^(n-3k+j-1)*3^j}};
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CROSSREFS
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Sequence in context: A150627 A150628 A106225 this_sequence A154108 A011965 A150629
Adjacent sequences: A127894 A127895 A127896 this_sequence A127898 A127899 A127900
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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), Feb 04 2007
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