72613domain: NPropertiesPrimalityPrimeyesAppears in sequencesa(n) = Sum_{x_1|n, x_2|n, ... , x_n|n} gcd(x_1,x_2, ... ,x_n).at n=7A344140Primes having square prime gaps to both neighbor primes.at n=16A353088Prime numbersat n=7179