2.5.4.9 RESEQUENCE Command
  The RESEQUENCE command allows you to resequence the
  line numbers of the program currently in memory. BASIC
  also changes all references to the old line numbers so they
  reference the new line numbers. You can specify a starting
  line number and a value by which to increase each subse-
  quent line number. The following command resequences the
  line numbers from 10 to 10000, making the first line number
  100 and increasing each subsequent line number by 20:
  RESEQUENCE 10-10000 100 STEP 20

  The RESEQUENCE command is not allowed on programs
  without line numbers.