360821domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumber of (n+3) X 5 0..1 matrices with each 4 X 4 subblock idempotent.at n=25A224562a(n) is the nearest integer to binomial(n,n/2) = n!/((n/2)!)^2.at n=21A318910Prime numbersat n=30809