1503377domain: NPropertiesPrimalityPrimeyesAppears in sequencesPrimes p such that sigma(p-1)+sigma(p+1) is prime.at n=23A067464a(n) = Sum_{1 <= x_1, x_2, x_3, x_4 <= n} gcd(x_1, x_2, x_3, x_4, n)^5.at n=16A372937Prime numbersat n=114406