Possible Clues:

• One is not even the first one
• It's not even considered, mathematically
• Perhaps one stranger goes around stupefied
• One is the first one to have 30 across in it
• Peculiar piece of music for 2017, say
• Three possibly dazed when taken in by stranger
• Seven or eleven
• 3 or 17, e.g
• It's not even considered mathematically
• One is the first such not to have even less feeling