A137111 Numbers n such that n and the square of n use only the digits 2, 5, 6, 7 and 8.

5, 25, 26, 75, 76, 85, 275, 525, 526, 725, 765, 766, 826, 875, 2585, 2785, 2875, 5275, 7525, 7665, 7666, 8525, 8675, 8765, 8865, 8875, 26875, 27525, 27725, 28675, 28785, 52525, 52785, 72576, 72585, 76526, 76585, 76665, 76666, 76725, 82875, 88785, 228665, 256266, 256275, 276725, 278725, 278865, 287725, 287865, 526525, 526865, 527525, 725725, 752785