134025domain: NAppears in sequencesNumber of unlabeled 3-element intersecting families (with not necessarily distinct sets) of an n-element set.at n=19A055484Numbers n for which 2n-1, 4n-1, 8n-1, 16n-1 and 32n-1 are primes.at n=14A124017Sum_{n>=0} a(n) * x^n / (n!)^2 = 1 / (1 - x * BesselI(0,2*sqrt(x))).at n=5A342182