6640200domain: NAppears in sequencesAmicable quadruples: the numbers b referred to in A036471.at n=6A036472a(n) = denominator of Sum_{i=1..n} 1/A031216(i).at n=11A375526a(n) = denominator of Sum_{i=1..n} 1/A031216(i).at n=12A375526