Normal irregular sudoku rules apply.
159 rule applies to every column. ie. digits in the Nth column indicate in which column the digit N is placed in the respective row (eg. if R3C2 is a 5, the fifth column in the third row (R3C5) must contain a 2).
Authors Note: the "HLOOKUP" in the title is referring to the Excel formula that returns which column a given value appears in.
Solution code: The digits of row 3 followed by the digits of row 6. (with a space between.)
on 12. March 2022, 09:19 by Offsuit Knave
fixed link to CTC app