User blog comment:Nayuta Ito/Brainfuck challenge/@comment-5529393-20160812141618

BF(88) >= 2^^^6 ++[->>>+[-<<+>>]<<[->>>+<+[-[>[[->+<]<[->>>+<<<]>>>[-<<+<+>>>]<-]<<-]>[-<++>]<<]<]<]>>>.

BF(89) > F_{w+1}(2^^^6 - 2) > G +++[->>>+[-<<+>>]<<[->>>+<+[-[>[[->+<]<[->>>+<<<]>>>[-<<+<+>>>]<-]<<-]>[-<++>]<<]<]<]>>>.

BF(90) > F_{w+1}^2(2^^^6 - 2) > F_{w+2}(2) ++++[->>>+[-<<+>>]<<[->>>+<+[-[>[[->+<]<[->>>+<<<]>>>[-<<+<+>>>]<-]<<-]>[-<++>]<<]<]<]>>>.

BF(91) > f_{w+2}(3) +++++[->>>+[-<<+>>]<<[->>>+<+[-[>[[->+<]<[->>>+<<<]>>>[-<<+<+>>>]<-]<<-]>[-<++>]<<]<]<]>>>.