{"schema":"vela.problem-packet.v0.1","problem":691,"statement":"Given $A\\subseteq \\mathbb{N}$ let $M_A=\\{ n \\geq 1 : a\\mid n\\textrm{ for some }a\\in A\\}$ be the set of multiples of $A$. Find a necessary and sufficient condition on $A$ for $M_A$ to have density $1$.","status":"open","seam":"raw","closureRoutes":[],"obligations":[],"attestations":[],"attempts":[],"velaLean":[],"oeis":[],"generated_note":"derived view; the signed event log is the source of truth (vela check / vela reproduce)"}