354081domain: NAppears in sequencesa(n) = a(1) + a(2) + ... + a(n-1) + a(m) for n >= 4, where m = n - 1 - 2^p and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), with a(1) = 1, a(2) = 2, and a(3) = 1.at n=19A049950a(n) is the least k such that the concatenations of k^i, i=0..j, are prime for j from 1 to n.at n=3A376027