Lewis & Short

Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.

Sēquăna, ae, f., one of the principal rivers of Gallia Celtica, the Seine, Caes. B. G. 1, 1; 7, 57; 7, 58; Mel. 3, 2, 4; masc., Plin. 4, 17, 31, § 105.
Hence,

    1. 1. Sēquă-ni, ōrum, m., the dwellers on the Sequana, Caes. B. G. 1, 1; 1, 2; 1, 9; 1, 10; 1, 31; 1, 35; 1, 44; 4, 10; 6, 12; 7, 66; Cic. Att. 1, 19, 2.
    2. 2. Sēquănus, a, um, adj., of or belonging to the Sequani: gens, Luc. 1, 425: ager, Plin. 14, 1, 3, § 18.
    3. 3. Sēquănī-cus, a, um, adj., of the Sequani: textrix. Mart. 4, 19, 1.