GCN Circular 3091
F. Bertoldi (RAIUB Bonn), D.A. Frail (NRAO), A. Weiss (IRAM), K.M. Menten (MPIfR Bonn), S. Kulkarni (Caltech), A. Soderberg (Caltech) report: We observed the position initially reported for the GRB 050306 X-ray afterglow by Perri et al. (GCN 3075), RA 18:49:14.0, Dec -09:09:10.4 (J2000), with the Max-Planck-Millimeter Bolometer (MAMBO-2) array at the IRAM 30-m telescope on 8 March 2005, between UT 8 and 9 h, and obtained a non-detection of S_nu(250 GHz,1.20mm) = 0.26 +/- 0.55 mJy (1 sigma error). The MAMBO-2 bolometer detectors cover 210-290 GHz (half power). The likely optical afterglow reported by D'Avanzo et al. (GCN 3089) is 1.9 arcsec from our pointing position, and well within our 10.7 arcsec FWHM beam.