A031151 Squares composed of digits {1,2,5}.

1, 25, 121, 225, 1225, 1521, 55225, 112225, 212521, 511225, 1525225, 2512225, 5112121, 5221225, 11122225, 152152225, 1111222225, 1155252121, 1222551225, 5225121225, 15211522225, 111112222225, 1212225222121, 1521115222225, 11111122222225, 122212251151225, 152111152222225

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• base

Comments

Includes all numbers of the form ((10^k-1)/3 + 2)^2 for k >= 1, of the form (37*(10^k - 1)/3 + 14)^2 for k >= 2, and of the form ((10^k - 1)/3 + 171152)^2 for k >= 10. - Andrew Howroyd, Oct 18 2024

Links

• Zhao Hui Du, Table of n, a(n) for n = 1..113
• Patrick De Geest, Squares containing at most three distinct digits, Index entries for related sequences

Crossrefs

Cf. A031153.

Programs

Mathematica

Select[Range[0,10^6]^2, SubsetQ[{1,2,5}, DeleteDuplicates[IntegerDigits[#]]]&] (* Stefano Spezia, Mar 09 2024 *)

Formula

a(n) = A031153(n)^2. - Andrew Howroyd, Oct 18 2024

Extensions

a(24)-a(27) from Stefano Spezia, Mar 09 2024