Usage: 2 forms in 2 verses
Form Translated As     In Verse(s)
επταπλάσιον seven-fold LXX.Isa.30.26
επταπλάσια seven-fold LXX.Prov.6.31

Liddell-Scott-Jones

ἑπταπλάσιος (heptaplasios, heptaplasiōn) seven-fold G:A

ἑπταπλάσιος-πλάσιος [πλᾰ], α, ον,

sevenfold, -πλασίῳ φαυλότερος [Refs 5th c.BC+] P. adverb -ιως[LXX]

ἑπταπλάσιος-πλᾰσίων, ον, genitive ονος, [Refs 4th c.AD+]

LSJ Scripture Refs: LXX.Ps.11.6*