Monotonic ordering of nonnegative differences 5^i-10^j, for 40>= i>=0, j>=0.

Terms

a(0) =0a(1) =4a(2) =15a(3) =24a(4) =25a(5) =115a(6) =124a(7) =525a(8) =615a(9) =624a(10) =2125a(11) =3025a(12) =3115a(13) =3124a(14) =5625a(15) =14625a(16) =15525a(17) =15615a(18) =15624a(19) =68125a(20) =77125a(21) =78025a(22) =78115a(23) =78124a(24) =290625a(25) =380625a(26) =389625a(27) =390525a(28) =390615a(29) =390624