Peter Kirk just emailed me that verse 41 in Psalm 118 has a digamma
at the beginning to indicate that it is the 6th section in the
psalm, the section beginning with the Hebrew letter 'vav',
transliterated into Greek as 'ouau'.
However, online editions of the Septuagint variously display either
a variant of omega or the letter v for the digamma. So the
equivalence should be between the Greek digamma and Hebrew vav, not
the omega and vav.