A018831 Numbers n such that n is a substring of its square in base 7 (written in base 10).

0, 1, 7, 30, 49, 285, 343, 911, 1900, 2208, 2401, 13962, 16807, 59763, 64098, 69128, 85880, 97734, 117649, 195032, 418341, 754422, 823543, 2162126, 2629229, 2790841, 3488518, 3842400, 4960401, 5764801, 7923812, 8559490, 15134882, 19765943, 31466333, 36415297

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• base

Crossrefs

Cf. A018826 (base 2), A018827 (base 3), A018828 (base 4), A018829 (base 5), A018830 (base 6), A018832 (base 8), A018833 (base 9), A018834 (base 10).

Programs

Mathematica

Select[Range[0, 10^7], StringContainsQ[IntegerString[#^2, 7], IntegerString[#, 7]] &] (* Paolo Xausa, Apr 05 2024 *)

Extensions

a(35)-a(36) from Pontus von Brömssen, Apr 04 2024