646379domain: NPropertiesPrimalityPrimeyesAppears in sequencesa(n) = numerator of b(n), where b(1) = 1, b(n) = Sum_{k=1..n-1} b(n-k) * H(k); H(k) = Sum_{j=1..k} 1/j, the k-th harmonic number.at n=8A128044Prime numbersat n=52550