L3685 in 2002 was Pentad by Tangent which used an 8x8 grid with the central 4 cells blocked out and 12 pentominoes used. Those of you who subscribed to The Magpie in the early days may remember seven Child's Play puzzles which were very hard. I only managed to solve two of them hence my dread when I saw the pseudonym on this puzzle. Thankfully this one was straight forward. So, welcome back Child's Play after 15 years!! Thanks.
I think it means what it says. Each of the numbers 1 to 9 occupies 5 contiguous cells. You need to divide the 45 cell grid into 9 contiguous groups of 5 cells.
Might have been better to say
"Each of the numbers 1 to 9 occupies one of nine distinct groups of five contiguous cells"? Or words to that effect...
I read it initially as nine digits in five cells.
Smellyharry, in the words of Alice in Wonderland (or is it Through the Looking-glass?) it might mean what it says, but it does not say what it means.
Muraria's wording is far better.
Apologies for the very basic question but are we meant to assume the series of 13 primes begins with 2? That is my operating assumption but based on that I can't find a way to fit the only possible answer to 7a into the grid in such a way that it allows for proper pentomino construction. (It is entirely possible I am either misunderstanding or miscalculating in some other way.)