This is a fun coding exercise.
Here's my answer to doing this:
$ 96,1,1,1,"begin(const last_index=w-1;);round(x/last_index*255);" rep_output_pdn_pal greys
Which gives me a 96 color palette txt file. This is the output for the most part.
; paint.net Palette File: Grayscale 96
; Color Format - AARRGGBB
; Colors: 96
FF000000
FF030303
FF050505
FF080808
FF0B0B0B
FF0D0D0D
FF101010
FF131313
FF151515
FF181818
FF1B1B1B
FF1E1E1E
FF202020
FF232323
FF262626
FF282828
FF2B2B2B
FF2E2E2E
FF303030
FF333333
FF363636
FF383838
FF3B3B3B
FF3E3E3E
FF404040
FF434343
FF464646
FF484848
FF4B4B4B
FF4E4E4E
FF515151
FF535353
FF565656
FF595959
FF5B5B5B
FF5E5E5E
FF616161
FF636363
FF666666
FF696969
FF6B6B6B
FF6E6E6E
FF717171
FF737373
FF767676
FF797979
FF7B7B7B
FF7E7E7E
FF818181
FF848484
FF868686
FF898989
FF8C8C8C
FF8E8E8E
FF919191
FF949494
FF969696
FF999999
FF9C9C9C
FF9E9E9E
FFA1A1A1
FFA4A4A4
FFA6A6A6
FFA9A9A9
FFACACAC
FFAEAEAE
FFB1B1B1
FFB4B4B4
FFB7B7B7
FFB9B9B9
FFBCBCBC
FFBFBFBF
FFC1C1C1
FFC4C4C4
FFC7C7C7
FFC9C9C9
FFCCCCCC
FFCFCFCF
FFD1D1D1
FFD4D4D4
FFD7D7D7
FFD9D9D9
FFDCDCDC
FFDFDFDF
FFE1E1E1
FFE4E4E4
FFE7E7E7
FFEAEAEA
FFECECEC
FFEFEFEF
FFF2F2F2
FFF4F4F4
FFF7F7F7
FFFAFAFA
FFFCFCFC
FFFFFFFF
For the OP, you could copy and paste this into a .txt file and place it into palette folder, and then open PDN.