129401356908domain: NAppears in sequencesa(n) = 4*a(n-1)+a(n-2), n>2; a(0)=1, a(1)=3, a(2)=12.at n=18A155179Lower (3/2)-midsequence of (F(2n)) and (F(2n+1)), where F=A000045 (Fibonacci numbers); see Comments.at n=26A387780Upper (3/2)-midsequence of (F(2n)) and (F(2n+1)), where F=A000045 (Fibonacci numbers); see Comments.at n=26A387781