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

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A009569 Expansion of e.g.f. sinh(log(1+tan(x))). 2
0, 1, -1, 5, -20, 136, -976, 8840, -88640, 1019776, -12933376, 181318400, -2767631360, 45821372416, -816582578176, 15596531778560, -317710534983680, 6876972491309056, -157606194409701376, 3812752893951672320, -97090584769337753600, 2596013487025352605696 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..430

FORMULA

a(n) ~ n! * (-1)^(n+1) * 4^n / Pi^(n+1). - Vaclav Kotesovec, Jan 23 2015

MATHEMATICA

CoefficientList[Series[(Tan[x]*(2 + Tan[x]))/(2*(1 + Tan[x])), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 23 2015 *)

With[{nmax = 50}, CoefficientList[Series[Sinh[Log[1 + Tan[x]]], {x, 0, nmax}], x]*Range[0, nmax]!] (* G. C. Greubel, Jan 21 2018 *)

PROG

(PARI) x='x+O('x^30); concat([0], Vec(serlaplace(sinh(log(1+tan(x)))))) \\ G. C. Greubel, Jan 21 2018

CROSSREFS

Sequence in context: A081067 A318250 A024066 * A061964 A133667 A318433

Adjacent sequences:  A009566 A009567 A009568 * A009570 A009571 A009572

KEYWORD

sign,easy

AUTHOR

R. H. Hardin

EXTENSIONS

Extended with signs by Olivier Gérard, Mar 15 1997

Terms a(20) and a(21) added by G. C. Greubel, Jan 21 2018

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 19 19:49 EST 2019. Contains 319309 sequences. (Running on oeis4.)