305424domain: NAppears in sequencesIn the "3x+1" problem, let 0 denote a halving step and 1 denote an x->3x+1 step. Then a(n) is obtained by writing the sequence of steps needed to reach 1 from 2n+1 and reading it as a decimal number.at n=4A125710Number of ways to place 2 nonattacking wazirs on an n X n board.at n=27A172225