Square in the Middle

The meta answer is 25. (The hint was: Find a number that comes next in a sequence hidden in the grid.)

No long clues, but you might have notice the following pairs of adjacent Across answers, symmetrically placed in the grid: FORMULA/LINER, CONNECT/SCORE, CLOUD/INNINGS and SWEET/CANDLES.

The puzzle's title, “Square in the Middle,” suggests the answer involves squares in the middle of each pair. The hint—that a number completes a hidden sequence—also suggests that the square is numerical in nature, like a square number (e.g., the result of multiplying a number by itself. Example: 10x10 = 100, so 100 is a square number).

But which square numbers? Ones that form well-known phrases when added to the words in each pair:

FORMULA [1] LINER = Formula 1/one-liner

CONNECT [4] SCORE = Connect Four/four score (as in the Gettysburg Address intro "Four score and seven years ago...")

CLOUD [9] INNINGS = cloud 9/nine innings

SWEET [16] CANDLES = Sweet 16/Sixteen Candles

1 (which is 1x1), 4 (which is 2x2), 9 (which is 3x3), and 16 (which is 4x4) are all consecutive square numbers. The next one in the sequence is 25 (which is 5x5), the meta answer that satisfies the puzzle's hint.

Super clever! Your metas are sometimes too twisty for me (not this one!) but your grids are always elegant.

Managed to escape a few rabbit holes to cross the finish line… clever, fun one!

Great puzzle/meta!

Too clever for me. I think I needed more help… perhaps to know that I needed to insert numbers into phrases? Or that the numbers themselves (not the sequence) were not actually present in the puzzle?

Very cool :)

That was fun!

Fun and elegant, thank you!

One note: “25” was accepted but “twenty-five” was not.