login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A009739 E.g.f. tan(x)*exp(x). 8
0, 1, 2, 5, 12, 41, 142, 685, 3192, 19921, 116282, 887765, 6219972, 56126201, 458790022, 4776869245, 44625674352, 526589630881, 5534347077362, 72989204937125, 852334810990332, 12424192360405961, 159592488559874302, 2547879762929443405, 35703580441464231912 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Robert Israel, Table of n, a(n) for n = 0..484

FORMULA

a(2n) = A009747(n), a(2n+1) = A003719(n).

E.g.f.: exp(x)*tan(x). - Zerinvary Lajos, Apr 05 2009

G.f.: 1/(x-1)/Q(0), where Q(k)= 1 - 1/x - (k+1)*(k+2)/Q(k+1); (continued fraction). - Sergei N. Gladkovskii, Apr 26 2013

G.f.: x/(1-x)/Q(0), where Q(k)= 1 - x - x^2*(k+1)*(k+2)/Q(k+1); (continued fraction). - Sergei N. Gladkovskii, Apr 26 2013

G.f.: G(0)*x/(1-x)^2, where G(k) = 1 - x^2*(k+1)*(k+2)/(x^2*(k+1)*(k+2) - (1-x)^2/G(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Jan 23 2014

a(n) ~ 2^(3/2 + n)*(exp(Pi) - (-1)^n)*exp(-Pi/2 - n)*Pi^(-1/2 - n)*n^(1/2 + n). - Robert Israel, Sep 22 2019

MAPLE

G(x):=exp(x)*tan(x): f[0]:=G(x): for n from 1 to 54 do f[n]:=diff(f[n-1], x) od: x:=0: seq(f[n], n=0..22 ); # Zerinvary Lajos, Apr 05 2009

# Alternative:

S:= series(exp(x)*tan(x), x, 51):

seq(coeff(S, x, j)*j!, j=0..50); # Robert Israel, Sep 22 2019

PROG

(PARI) x='x+O('x^66); concat([0], Vec(serlaplace(tan(x)*exp(x)))) \\ Joerg Arndt, Apr 26 2013

CROSSREFS

Sequence in context: A203151 A140440 A005664 * A062272 A215789 A127137

Adjacent sequences:  A009736 A009737 A009738 * A009740 A009741 A009742

KEYWORD

nonn,easy

AUTHOR

R. H. Hardin

EXTENSIONS

Extended and signs tested by Olivier Gérard, Mar 15 1997

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 26 14:08 EST 2020. Contains 331280 sequences. (Running on oeis4.)