Sequence is remembering kanji in a word compound or sentence in. You may not be able to recall the character in isolation but once you start to write it in sequence, it might come back to you.
1 I associate the kanji with other kanji in the sequence it’s often used in.
e.g.2 新幹線（しんかんせんshinkansen or bullet train）
e.g. 3 勉強（べんきょうstudy）
2 I place the new kanji in a sentence and remember it in that context.