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A000772
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E.g.f. exp(tan(x) + sec(x) - 1).
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4
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1, 1, 2, 6, 23, 107, 583, 3633, 25444, 197620, 1684295, 15618141, 156453857, 1683050189, 19344093070, 236497985706, 3063827565763, 41916787157011, 603799270943519, 9132945141812301, 144708157060239704, 2396568154933265024, 41403636316192616995
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OFFSET
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0,3
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COMMENTS
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The number of elevated increasing binary trees. There is no restriction on the outdegree at the root. - Wenjin Woan, Jan 09 2008
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LINKS
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T. D. Noe, Table of n, a(n) for n = 0..100
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FORMULA
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a(n)=sum(k=1..n, A147315(n-1,k-1)), n>0, a(0)=1. [From Vladimir Kruchinin, Mar 10 2011]
a(n) = D^n(exp(x)) evaluated at x = 0, where D is the operator (1+x+x^2/2!)*d/dx. Cf. A000110 and A094198. See also A185422. - Peter Bala, Nov 25 2011
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MATHEMATICA
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nn = 25; Range[0, nn]! CoefficientList[Series[Exp[Tan[x] + Sec[x] - 1], {x, 0, nn}], x] (* T. D. Noe, Jun 20 2012 *)
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CROSSREFS
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Sequence in context: A187761 A130908 A200404 * A200405 A200403 A113226
Adjacent sequences: A000769 A000770 A000771 * A000773 A000774 A000775
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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