2462400domain: NAppears in sequencesNumber of pairs of 2 X 2 matrices (X,Y) over Z/nZ such that X*Y = 0 and Y*X <> 0.at n=18A338099a(n) is the numerator of the median abundancy index of the first 2^n + 1 positive integers.at n=22A353615Expansion of e.g.f. 1 / (1 + x^2 * log(1 - x))^2.at n=9A375639