The New York Times reports that Anthropic set a price range of $70 to $78 a share for its initial public offering, valuing the A.I. company at $1.26 trillion to $1.41 trillion — below the $2 trillion bankers floated in the summer but above its $900 billion private valuation, and set at a volatile moment for stocks. Anthropic, founded by former OpenAI employees including Dario and Daniela Amodei, would be the first frontier lab public market investors can buy into, and its founders have pledged to donate 80 percent of their holdings to charity.