1626743domain: NAppears in sequencesa(n) = Sum_{k|n} a(k) a(n-k) for n >= 2, a(0)=0, a(1)=1.at n=28A097438a(n) = Sum_{k|n} a(k) a(n-k) for n >= 2, a(0)=0, a(1)=1.at n=29A097438