149663397domain: NAppears in sequencesNumbers n > 1 such that 2^m == 1 (mod n^2), where m = A002326((n-1)/2).at n=28A265630Numbers n > 1 such that 2^lambda(n) == 1 (mod n^2), where lambda(n) is the Carmichael lambda function (A002322).at n=29A291961