6185169domain: NAppears in sequencesSquare such that the next three squares also having a square digit sum.at n=21A068834Let the n-th Carmichael number A002997(n) = p1*p2*...*pr, where p1 < p2 < ... < pr are primes. Then a(n) = (p1-1) * (p1*p2*...*pr - 1)^(r-2) / ((p2-1)*...*(pr-1)).at n=23A180044