503132domain: NAppears in sequencesa(1) = 1; a(n+1) = floor(sqrt(Sum_{k=1..n} a(k)^2)).at n=41A067859Number of n-bead necklaces labeled with numbers -1..1 not allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2.at n=17A209108