224107domain: NAppears in sequencesa(n) = a(1) + a(2) + ... + a(n-1) - a(m) for n >= 4, where m = 2*n - 2 - 2^(p+1) and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = 1, a(2) = 2 and a(3) = 4.at n=20A049915Number of (n+4)X5 0..1 matrices with each 5X5 subblock idempotent.at n=16A224683