A030484 Squares composed of digits {2,5,6}.

25, 225, 256, 625, 5625, 55225, 225625, 265225, 266256, 525625, 26265625, 56625625, 525555625, 556252225, 5252625625, 255555525625, 265652622225, 6255626265625, 225255552522256, 562222665225225, 5222566262655625, 22225226555625625, 62566655262225625, 65552556565552225

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• base

Comments

Each term is either 25 or 56 mod 100 (which is used in the Mathematica program below to improve the search speed). - Harvey P. Dale, Jul 02 2016

Links

• Zhao Hui Du, Table of n, a(n) for n = 1..44
• Patrick De Geest, Squares containing at most three distinct digits, Index entries for related sequences.
• Hisanori Mishima, Sporadic tridigital solutions.

Crossrefs

Cf. A030486.

Programs

Mathematica

Select[Flatten[Table[{FromDigits/@(Join[#,{2,5}]&/@Tuples[{2,5,6},n]), FromDigits/@ (Join[#,{5,6}]&/@Tuples[{2,5,6},n])},{n,0,14}]], IntegerQ[ Sqrt[#]]&]//Sort (* Harvey P. Dale, Jul 02 2016 *)

Formula

a(n) = A030486(n)^2. - Elmo R. Oliveira, Jul 16 2025

Extensions

Extended and corrected by Patrick De Geest, May 08 2000