156905298045domain: NAppears in sequencesa(n) = 5*3^n.at n=22A005030Third column of triangle A067402.at n=12A0674033rd binomial transform of (1,2,0,0,0,0,0,0,...).at n=21A081038a(0)=1, a(1)=5, a(n) = -3*a(n-1), n>1.at n=23A084244a(n) is the least k that has exactly n divisors whose arithmetic derivative is odd.at n=23A363483