[ 1 & ]                is odd       ( n --> b )

  [ 0 swap
   [ dip 1+
     10 / dup
     0 = until ]
    drop ]               is digits    ( n --> n )

  [ dup dup size
    dup odd iff
      [ dup 1 - 2 /
        dip
          [ 1 + 2 / peek
            over ]
        peek + ]
    else
      [ 2 / peek ]
    join ]               is nextfusc  ( [ --> [ )

  say "First 61 terms." cr
  ' [ 0 1 ]
  59 times nextfusc
  witheach [ echo sp ]
  cr cr
  say "Terms where the digit count increases." cr
  say "fusc(0) = 0" cr
  1 ' [ 0 1 ]
  [ nextfusc
    dup -1 peek digits
    rot 2dup > iff
      [ drop swap
        say "fusc("
        dup -1 peek echo
        say ") = "
        dup size 1 - echo cr ]
    else [ nip swap ]
    dup size 1000000 = until ]
  2drop