This is a free “warm-up” puzzle; Season 4 subscribers will see today’s main puzzle in the same style posted at 9:05 AM PT.

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between number entry and shading modes.)

Theme: Triangular Numbers

Author/Opus: This is the 127th puzzle from our contributing puzzlemaster JinHoo Ahn.

Rules: Fill some cells with numbers 1-4 so that each row and column contains each number from 1 to 4 exactly once as well as one empty cell. Numbers outside of the grid indicate the sum of all numbers in the first connected group in that direction as in a Japanese Sums puzzle.

See also this example with the numbesr 1 to 4 and two empty cells:

Difficulty: 1 star

Time Standards (highlight to view): Grandmaster = 0:30, Master = 0:45, Expert = 1:30

Solution: PDF and solving animation.

Note: Follow this link for other Japanese Sums puzzles. Also, visit this page to purchase all of the puzzles from the 30th World Puzzle Championship including some Easy as Japanese Sums.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our Week 6 Discussion post on the GMPuzzles Discord.