Frank L. Henderson, 23, was sentenced to two consecutive terms of 15 years to life in prison yesterday for his part in a series of armed rapes, armed kidnapings, armed robberies and related offenses that he and four other persons committed in October, 1975.

Judge Nicholas S. Nunzie of D.C. Superior Court told Henderson that he should have "stayed with boxing" - a sport in which the defendant had begun as an amateur - rather than joining his codefendants, all of whom have been convicted of, or pleaded guilty to, the crimes for which Henderson was sentenced yesterday.

Nunzio ordered that Henderson serve 15 years to life for one count of armed kidnaping and an additional 15 years to life for one count of armed rape. He gave lesser terms - to run concurrently with the major penalties - for several armed robberies and related crimes.

The sentence means that Henderson must serve a minimum of 30 years before he is eligible for parole consideration.

Henderson was the fourth of five defendants sentenced. The others, who pleaded guilty or were tried separately, are Larry P. Hallman, 28, sentenced to 49 years to life, and Eddie Wilson, 19, and Warren Peters, 20, both serving 28 years to life.

A fifth defendant, Raymond Paris, 18, was permitted to plead guilty to one count of second-degree murder in return for his testimony against the others.

Paris, Hallman, Peters and Wilson were convicted of the murders of Curtis Arrington, 23, and Lois Ann Davis, 16, in an apartment at 1200 Delaware Ave. SW on Oct. 22, 1975. Henderson was not charged in that case.