612535domain: NAppears in sequencesa(n) = Sum_{k=0..n-1} sigma(2k+1)*sigma_3(n-k).at n=20A081860Number of 5-tuples (v1,v2,v3,v4,v5) of nonnegative integers less than n such that v1 <= v5, v2 <= v5, v2 <= v4 and v3 <= v4.at n=20A085461