Sorry for the error in my last contribution. Of course A282178 does not start with number 1. I wanted to say that the elements of A282178 are in the column with number 1. The primes of A330339 are equivalent to 1 modulo 4. The primes of A282178 are equivalent to 3 modulo 4. If n is odd p = prime(n) belongs to A282178 if 2*(s1(n) - s2(n)) + p = 1 p = prime(n) does not belong to A330339 Where s1(n) = sum(prime(k) for k=1,3,5,...,n-2) and s2(n) = sum(prime(k) for k=2,4,6,...,n-1) If n is even p = prime(n) belongs to A282178 if 2*(s1(n) - s2(n)) - p = 1 p = prime(n) belongs to A330339 if 2*(s1(n) - s2(n)) - p = -1 Where s1(n) = sum(prime(k) for k=1,3,5,...,n-1) and s2(n) = sum(prime(k) for k=2,4,6,...,n-2) Walter