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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A167199 First column of A167196. 2
 1, -2, 7, -36, 246, -2100, 21510, -257040, 3510360, -53933040, 920694600 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Limiting ratio 2+n*a(n-1)/a(n) converges to A002193. LINKS FORMULA Conjecture: E.g.f.: 2/(2+4*x+x^2) = G(0)/(1+x) where  G(k) = 1 - x/((1+x) - x*(1+x)/(x - (1+x)*2/G(k+1) )); (recursively defined continued fraction). - Sergei N. Gladkovskii, Dec 28 2012. a(n) ~ n! * (-1)^n * (1+sqrt(2))/2 * (1+1/sqrt(2))^n. - Vaclav Kotesovec, Oct 08 2013 MATHEMATICA CoefficientList[Series[2/(2+4*x+x^2), {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Oct 08 2013 *) CROSSREFS Cf. A167196, A002193. Sequence in context: A095793 A029768 A180271 * A007889 A125033 A034430 Adjacent sequences:  A167196 A167197 A167198 * A167200 A167201 A167202 KEYWORD more,sign AUTHOR Mats Granvik, Oct 30 2009 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.

Last modified June 19 13:05 EDT 2021. Contains 345129 sequences. (Running on oeis4.)