|
Search: id:A000831
|
|
|
| A000831 |
|
Expansion of (1+tan x)/(1-tan x). |
|
+0
4
|
|
| 1, 2, 4, 16, 80, 512, 3904, 34816, 354560, 4063232, 51733504, 724566016, 11070525440, 183240753152, 3266330312704, 62382319599616, 1270842139934720, 27507470234550272, 630424777638805504
(list; graph; listen)
|
|
|
OFFSET
|
0,2
|
|
|
REFERENCES
|
D. Dumont, Further triangles of Seidel-Arnold type and continued fractions related to Euler and Springer numbers, Adv. Appl. Math., 16 (1995), 275-296.
|
|
LINKS
|
R. J. Mathar, Table of n, a(n) for n = 0..83
|
|
FORMULA
|
E.g.f.: tan(x+Pi/4).
|
|
EXAMPLE
|
(1+tan x)/(1-tan x)=1+2x/1!+4x^2/2!+16x^3/3!+80x^4/4!+512x^5/5!+...
|
|
MAPLE
|
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
|
|
PROGRAM
|
(PARI) a(n)=if(n<1, !n, n!*polcoeff(1+2/(1/tan(x+x*O(x^n))-1), n))
|
|
CROSSREFS
|
Cf. A002436(n)=A000831(2n).
a(2n+1) = A012393(n).
Sequence in context: A027436 A025225 A115125 this_sequence A000090 A013115 A007171
Adjacent sequences: A000828 A000829 A000830 this_sequence A000832 A000833 A000834
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
njas
|
|
|
Search completed in 0.002 seconds
|
