A031152 Squares composed of digits {2,4,5}.

4, 25, 225, 4225, 55225, 442225, 4545424, 5452225, 42445225, 44422225, 544522225, 2224254244, 4424245225, 4444222225, 4554225225, 54445222225, 55255554225, 444242245225, 444442222225, 5444452222225, 44442422245225, 44444422222225, 544444522222225

Offset

1,1

Comments

Includes all numbers of the form (2*(10^k-1)/3 - 1)^2 for k >= 1, of the form (2*(10^k - 1)/3 - 151)^2 for k >= 4, and of the form (7*(10^k-1)/3 + 4)^2 for k >= 2. - Andrew Howroyd, Oct 18 2024

Links

Zhao Hui Du, Table of n, a(n) for n = 1..106

Patrick De Geest, Squares containing at most three distinct digits, Index entries for related sequences

Formula

a(n) = A031154(n)^2. - Andrew Howroyd, Oct 18 2024

Mathematica

Flatten[Table[Select[FromDigits/@Tuples[{2, 4, 5}, n], IntegerQ[Sqrt[#]]&], {n, 14}]] (* Harvey P. Dale, Oct 07 2013 *)

Crossrefs

Cf. A031154.

Sequence in context: A302608 A340337 A001247 * A010845 A087660 A121660

Adjacent sequences: A031149 A031150 A031151 * A031153 A031154 A031155

Keyword

nonn,base

Author

Patrick De Geest

Extensions

Extended and corrected by author 03/2000.

a(22)-a(23) from Alois P. Heinz, Apr 01 2015

Status

approved