387977domain: NPropertiesPrimalityPrimeyesAppears in sequencesa(n) = Sum_{i=1..n, j=1..n, gcd(i,j)=1} (n+1-i)*(n+1-j).at n=38A115004a(n) = A115004(2n+1).at n=19A331759Prime numbersat n=32908