Logic Masters Deutschland e.V.

Rules

• Standard sudoku rules apply
• A "prime rib" is a sequence of digits that alternates between prime (2,3,5,7) and non-prime numbers, with both ends being prime numbers.
• A prime rib sandwich consists of a prime rib as its filling, stuffed between any two other digits (prime or not) that serve as the bread.
• The numbers on the left and top of the grid represent the sum of the digits of the filling of the largest prime rib sandwich in the row/column.
• There will be no clues for open-faced sandwiches -- there must be at least one digit on each side of the prime rib acting as the bread.
• A zero (0) clue means that the row/column has no valid prime rib sandwiches.

Penpa link
NOTE: One clue is an inequality

Examples

• In the two valid rows, the bread is green and the filling is yellow. Clues refer to the sum of the yellow cells.
• The red cells in the third example are not a valid sandwich because there is no digit to the left of the prime rib.
• In the final example there are two sandwiches of the same size. Because a clue would be ambiguous in this case, a row with this pattern would never be clued.

Solution code: Row 4 and Column 4 (18 digits, no spaces or separators)