3592859domain: NPropertiesPrimalityPrimeyesAppears in sequencesa(n) = 5*b_5(n)+4, where b_5 lists the indices of zeros of the sequence A261305: u(n) = abs(u(n-1)-gcd(u(n-1),5*n-1)), u(1) = 1.at n=7A186257Prime numbersat n=256237