121619domain: NAppears in sequencesTruncated square pyramid numbers: a(n) = Sum_{k = n..2*n} k^2.at n=37A050409a(n) = (Product_{i=0..4}(i*n+2) - Product_{i=0..4}(-i*n-1))/(4*n+3).at n=18A274119Products p*q*r of three distinct primes such that s=(p*q) mod r, t=(p*r) mod q and u=(q*r) mod p, and s+t+u are all prime.at n=27A338705