up to 10^1: 9
up to 10^2: 10
up to 10^3: 14
up to 10^4: 17
up to 10^5: 17
up to 10^6: 17
up to 10^7: 18
up to 10^8: 18
found at or above 1000: 1306 1676 2427 2646798