*DECK INDXA
      SUBROUTINE INDXA (I, IR, IDXA, NA)
C***BEGIN PROLOGUE  INDXA
C***SUBSIDIARY
C***PURPOSE  Subsidiary to BLKTRI
C***LIBRARY   SLATEC
C***TYPE      INTEGER (INDXA-I)
C***AUTHOR  (UNKNOWN)
C***SEE ALSO  BLKTRI
C***ROUTINES CALLED  (NONE)
C***COMMON BLOCKS    CBLKT
C***REVISION HISTORY  (YYMMDD)
C   801001  DATE WRITTEN
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C   900402  Added TYPE section.  (WRB)
C***END PROLOGUE  INDXA
      COMMON /CBLKT/  NPP        ,K          ,EPS        ,CNV        ,
     1                NM         ,NCMPLX     ,IK
C***FIRST EXECUTABLE STATEMENT  INDXA
      NA = 2**IR
      IDXA = I-NA+1
      IF (I-NM) 102,102,101
  101 NA = 0
  102 RETURN
      END