Monotonic ordering of nonnegative differences 4^i-7^j, for 40>= i>=0, j>=0.

Terms

a(0) =0a(1) =3a(2) =9a(3) =15a(4) =57a(5) =63a(6) =207a(7) =249a(8) =255a(9) =681a(10) =975a(11) =1017a(12) =1023a(13) =1695a(14) =3753a(15) =4047a(16) =4089a(17) =4095a(18) =13983a(19) =16041a(20) =16335a(21) =16377a(22) =16383a(23) =48729a(24) =63135a(25) =65193a(26) =65487a(27) =65529a(28) =65535a(29) =144495