[seqfan] Generating function for A000992

[N. J. A. Sloane]

Dear Sequence Fans,
A correspondent asks if there is a formula or g.f. for A000992:

> Date: Tue, 20 Dec 2011 12:50:41 +0100
> From: Jan Schwientek <Jan.Schwientek at itwm.fraunhofer.de>
> I'm PhD student and interested in an explicit representation and/or
> generating function for the integer sequence A000992

Can anyone help him?
Neil