1706251domain: NPropertiesPrimalityPrimeyesAppears in sequencesSequence a_n arising in enumeration of arrays of directed blocks (see Quaintance reference for precise definition).at n=10A129878Primes of the form sum_{j=1..n} (-1)^j *prime(j)*prime(j+1).at n=23A197422Prime numbersat n=128572