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Search: id:A000831
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| A000831 |
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Expansion of (1+tan x)/(1-tan x). |
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+0
5
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| 1, 2, 4, 16, 80, 512, 3904, 34816, 354560, 4063232, 51733504, 724566016, 11070525440, 183240753152, 3266330312704, 62382319599616, 1270842139934720, 27507470234550272, 630424777638805504
(list; graph; listen)
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OFFSET
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0,2
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REFERENCES
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D. Dumont, Further triangles of Seidel-Arnold type and continued fractions related to Euler and Springer numbers, Adv. Appl. Math., 16 (1995), 275-296.
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LINKS
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R. J. Mathar, Table of n, a(n) for n = 0..83
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FORMULA
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E.g.f.: tan(x+Pi/4).
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EXAMPLE
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(1+tan x)/(1-tan x)=1+2x/1!+4x^2/2!+16x^3/3!+80x^4/4!+512x^5/5!+...
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MAPLE
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A000831 := (1+tan(x))/(1-tan(x)) : for n from 0 to 200 do printf("%d %d ", n, n!*coeftayl(A000831, x=0, n)) ; end: - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 19 2006
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PROGRAM
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(PARI) a(n)=if(n<1, !n, n!*polcoeff(1+2/(1/tan(x+x*O(x^n))-1), n))
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CROSSREFS
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Bisections: A002436 and A012393.
Cf. A155100.
Sequence in context: A027436 A025225 A115125 this_sequence A000090 A013115 A007171
Adjacent sequences: A000828 A000829 A000830 this_sequence A000832 A000833 A000834
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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