This Bible contradiction is from the Skeptic's Annotated Bible.
Abiathar was the son of Ahimelech.
1 Samuel 22:20 View context
And one of the sons of Ahimelech the son of Ahitub, named Abiathar, escaped, and fled after David.
1 Samuel 23:6 View context
And it came to pass, when Abiathar the son of Ahimelech fled to David to Keilah, [that] he came down [with] an ephod in his hand.
Abiathar was the father of Ahimelech.
2 Samuel 8:17 View context
And Zadok the son of Ahitub, and Ahimelech the son of Abiathar, [were] the priests; and Seraiah [was] the scribe;
1 Chronicles 18:16 View context
And Zadok the son of Ahitub, and Abimelech the son of Abiathar, [were] the priests; and Shavsha was scribe;
1 Chronicles 24:6 View context
And Shemaiah the son of Nethaneel the scribe, [one] of the Levites, wrote them before the king, and the princes, and Zadok the priest, and Ahimelech the son of Abiathar, and [before] the chief of the fathers of the priests and Levites: one principal household being taken for Eleazar, and [one] taken for Ithamar.