login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A084253 a(n) is the denominator of the coefficient of z^(2n-1) in the Maclaurin expansion of Sqrt[Pi]Erfi[z]. 1

%I #8 Jan 12 2017 20:12:16

%S 1,3,5,21,108,660,4680,37800,342720,3447360,38102400,459043200,

%T 5987520000,84064780800,1264085222400,20268952704000,345226033152000,

%U 6224529991680000,118443913555968000,2372079457972224000

%N a(n) is the denominator of the coefficient of z^(2n-1) in the Maclaurin expansion of Sqrt[Pi]Erfi[z].

%C Numerators are unity for n>2.

%C Same as A007680/2 for n>2.

%H G. C. Greubel, <a href="/A084253/b084253.txt">Table of n, a(n) for n = 1..445</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Erfi.html">Erfi</a>

%F a(n) = (2*n-1)*(n-1)!/2 for n>2.

%t Join[{1, 3}, Table[(2*n - 1)*n!/(2*n), {n,3,50}]] (* or *) Denominator[ CoefficientList[Series[Sqrt[Pi]*Erf[t], {t, 0, 10}], t]][[2 ;; ;; 2]] (* _G. C. Greubel_, Jan 12 2017 *)

%o (PARI) concat([1,3], for(n=3, 50, print1((2*n-1)*n!/(2*n), ", "))) \\ _G. C. Greubel_, Jan 12 2017

%Y Cf. A007680.

%K nonn,easy

%O 1,2

%A _Eric W. Weisstein_, May 23 2003

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)