Re: Concatenating the attribute values of ancestors

you should get an error about using an undefined param
            <xsl:with-param name="anestors"
                                    ^


However you don't need all that recursion it looks like a single Xpath

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                version="2.0">


<xsl:template match="*">
  <xsl:copy>
   <xsl:copy-of select="@*"/>
    <xsl:attribute name="newseq"
     select="string-join(ancestor-or-self::*/(if (@seq) then string(@seq) else '0'),'')"/>
    <xsl:apply-templates/>
   </xsl:copy>
</xsl:template>     

</xsl:stylesheet>

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