A014889 n is equal to the number of 5s in all numbers <= n written in base 7.

761664, 817499, 817500, 817507, 817508, 819609, 823543, 1585207, 1641042, 1641043, 1641050, 1641051, 1643152, 1647086, 2408750, 2464585, 2464586, 2464593, 2464594, 2466695, 2470629, 3232293, 3288128, 3288129, 3288136, 3288137, 3290238, 3294172, 4055836, 4111671, 4111672, 4111679, 4111680, 4113781