"You should fast the thirteenth, fourteenth and fifteenth." (Hasan) Abu 'Abdur-Rahman (An-Nasai) said: This is a mistake, it is not a narration of Bayan; perhaps Sufyan said: "It was narrated to us by two (Ithnan)" and the 'Alif was dropped so it became Bayan. (Using translation from Nasāʾī 2425)
أَنَّ النَّبِيَّ ﷺ قَالَ لِرَجُلٍ «عَلَيْكَ بِصِيَامِ ثَلَاثَ عَشْرَةَ وَأَرْبَعَ عَشْرَةَ وَخَمْسَ عَشْرَةَ» قَالَ أَبُو عَبْدِ الرَّحْمَنِ هَذَا خَطَأٌ لَيْسَ هَذَا مِنْ حَدِيثِ بَيَانٍ وَلَعَلَّ سُفْيَانَ قَالَ حَدَّثَنَا اثْنَانِ فَسَقَطَتِ الْأَلِفُ فَصَارَ بَيَانٌ