a(1)=1, a(2)=6; for n > 2, a(n) is the smallest unused positive number such that gcd(a(n-1)+n, a(n)) > 1, gcd(a(n-1), a(n)) > 1, and gcd(n, a(n)) > 1.

A349492

a(1)=1, a(2)=6; for n > 2, a(n) is the smallest unused positive number such that gcd(a(n-1)+n, a(n)) > 1, gcd(a(n-1), a(n)) > 1, and gcd(n, a(n)) > 1.