Normal sudoku rules apply.
Each number next to a row refers to the square with a “5” in that row, and is the sum of all squares that are orthogonally adjacent to that square. Each number above a column refers to the square with a “4” in that column, and is the sum of all squares that are orthogonally adjacent to that square.
Example:
The puzzle:
Solving online: penpa
Solution code: Row 5 then row 6. Left to right, no gaps between numbers.
on 19. August 2020, 10:31 by Thorsby
Added link
on 16. August 2020, 13:25 by Thorsby
added arithmetic label
on 16. August 2020, 12:07 by Thorsby
Changed column to row in solution code. Sorry!