login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A013528 Numerator of [x^(2n)] of the Taylor series sech(cosec(x)-cot(x)) = 1 -x^2/8 -x^4/128 +x^6/15360 +19*x^8/294912 +25031*x^10/3715891200+... . 1
1, -1, -1, 1, 19, 25031, 18421, -622177, -283401163, -24826632949, -2243454779, 4882905709651, 43798187793808543, -46704901267812186793, -5325187532598955153807 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

The e.g.f. related to x/2, sech(cosec(x)-cot(x)) = 1 -1*x^2/(2^2*2!) -3*x^4*(2^4*4!) +3*x^6/(2^6*6!) +665*x^8/(2^8*8!) +.. is (up to signs) apparently provided by A009011.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..200

MATHEMATICA

Numerator[Take[CoefficientList[Series[Sech[Csc[x] - Cot[x]], {x, 0, 50}], x], {1, -1, 2}]] (* G. C. Greubel, Nov 12 2016 *)

CROSSREFS

Sequence in context: A125043 A249907 A233105 * A172762 A203703 A068734

Adjacent sequences:  A013525 A013526 A013527 * A013529 A013530 A013531

KEYWORD

sign,frac

AUTHOR

Patrick Demichel (patrick.demichel(AT)hp.com)

EXTENSIONS

Name edited by R. J. Mathar, Dec 20 2011

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified September 24 04:27 EDT 2017. Contains 292403 sequences.