This is what you want, isn't it?recurrence!((a,n)=>a[n-1]+a[n-2])(1,1).until!(a=>a>=40000)()
That is, the meat of it. The full line: writeln(recurrence!((a,n)=>a[n-1]+a[n-2])(1,1).until!(a=>a>=40000)().filter!(a=>a%2==0)().reduce!((a,b)=>a+b)()) -- Simen
