Numbers whose base-10 representation has the same nonzero number of 1's and 4's.

Terms

a(0) =14a(1) =41a(2) =104a(3) =124a(4) =134a(5) =140a(6) =142a(7) =143a(8) =145a(9) =146a(10) =147a(11) =148a(12) =149a(13) =154a(14) =164a(15) =174a(16) =184a(17) =194a(18) =214a(19) =241a(20) =314a(21) =341a(22) =401a(23) =410a(24) =412a(25) =413a(26) =415a(27) =416a(28) =417a(29) =418