212159

Appears in sequences

• Odd prime-proof numbers (A118118) not ending in 5.at n=0A143641
• Numbers ending in 1, 3, 7 or 9 such that changing any one decimal digit produces a composite number.at n=0A186694
• a(n) where a(n)=-a(-n), a(1)=a(2)=a(3)=a(4)=1, and a(n+2)*a(n-2) = a(n+1)*a(n-1) - c(n)*a(n)^2 where c(3*k)=-2, else c(n)=1.at n=17A320769