User blog comment:Nayuta Ito/Brainfuck challenge/@comment-5529393-20160812101907

B(54) >= 2^^^4 - 2 +++[>+[>+[>+[>++<-]>[<+>-]<<-]>[<+>-]<<-]>[<+>-]<<-]>.

B(55) >= 2^^^5 - 2 ++++[>+[>+[>+[>++<-]>[<+>-]<<-]>[<+>-]<<-]>[<+>-]<<-]>.

B(56) >= 2^^^6 - 2 +++++[>+[>+[>+[>++<-]>[<+>-]<<-]>[<+>-]<<-]>[<+>-]<<-]>.

B(57) >= 2^^^7 - 2 ++++++[>+[>+[>+[>++<-]>[<+>-]<<-]>[<+>-]<<-]>[<+>-]<<-]>.

B(58) >= 2^^^8 - 2 +++++++[>+[>+[>+[>++<-]>[<+>-]<<-]>[<+>-]<<-]>[<+>-]<<-]>.