536805376domain: NAppears in sequencesa(n) = 2*a(n-1) + 2*a(n-2) - 4*a(n-3), a(1) = 0, a(2) = 0, a(3) = 8.at n=27A297619Lesser member of Carmichael's variant of amicable pair: numbers k < m such that s(k) = m and s(m) = k, where s(k) = A371418(k).at n=19A371419