5945425920domain: NAppears in sequencesRatios of successive terms are 1,2,2,2,3,4,4,4,5,6,6,6,7,...at n=16A004528Expansion of e.g.f. x^2/(1-4*x).at n=9A052670a(n) = Product_{j=1..n} Product_{k=1..n} gcd(j,k).at n=8A092287Denominators arising in the expansion of Sum_{k>=1} (1/(4k^2-1)^n) in even powers of Pi.at n=10A382783