a(n) = Card{ (x,y,z,u,v) | lcm(x,y,z,u,v)=n }.

Terms

a(0) =1a(1) =31a(2) =31a(3) =211a(4) =31a(5) =961a(6) =31a(7) =781a(8) =211a(9) =961a(10) =31a(11) =6541a(12) =31a(13) =961a(14) =961a(15) =2101a(16) =31a(17) =6541a(18) =31a(19) =6541a(20) =961a(21) =961a(22) =31a(23) =24211a(24) =211a(25) =961a(26) =781a(27) =6541a(28) =31a(29) =29791