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Search: id:A046885
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| 1, 4, 18, 85, 411, 2013, 9933, 49236, 244750, 1218888, 6077644, 30329434, 151439158, 756452890, 3779590010, 18888255205, 94405918355, 471899946985, 2359022096225, 11793343217935, 58960151969255, 294776293579255
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OFFSET
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1,2
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FORMULA
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a(n) = 2*5^(n-1) - A046714(n-1) = (A046748(n) - 5^(n-1))/2; G.f.: x*(2-c(x))/(1-5*x), c(x): = g.f. for A000108 (Catalan numbers).
i) Inhomogeneous recursion: a(n) = 5*a(n-1) - C(n-1), n >= 2, a(1)=1; C(n)=A000108(n) (Catalan). ii) Homogeneous recursion: a(n) = (3*(3*n-2)/n)*a(n-1) - (10*(2*n-3)/n)*a(n-2), n >= 3, a(1)=1, a(2)=4.
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CROSSREFS
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Cf. A046658, A046714, A046748, A000108.
Sequence in context: A007859 A085923 A110166 this_sequence A055834 A079567 A030278
Adjacent sequences: A046882 A046883 A046884 this_sequence A046886 A046887 A046888
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KEYWORD
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easy,nonn
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AUTHOR
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Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de)
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