53557domain: NAppears in sequencesE.g.f.: 1/sqrt(1+x^2 - 2*x*cosh(x)).at n=7A205570Numbers m such that m^2 divides 2^k - 1 for some k, 0 < k <= m.at n=23A246503Composite numbers for which A324644(n)/A324198(n) = 2 and sigma(n) == 2 (mod 4).at n=41A371082