A368049 Perfect squares whose decimal expansion consists of k > 1 digits, k-1 of which are equal.

16, 25, 36, 49, 64, 81, 100, 121, 144, 225, 400, 441, 484, 676, 900, 1444, 10000, 40000, 44944, 90000, 1000000, 4000000, 9000000, 100000000, 400000000, 900000000, 10000000000, 40000000000, 90000000000, 1000000000000, 4000000000000, 9000000000000, 100000000000000

Offset: 1

Author

José Hernández, Dec 09 2023

Keywords

• nonn
• base
• easy

Comments

The terms > 90000 are of one of the following three forms: 10^(2*j), 4*10^(2*j) or 9*10^(2*j) where j is an integer >= 3.

See Gica/Panaitopol link for proof of above comment. - Ray Chandler, Jan 16 2024

Links

• Ray Chandler, Table of n, a(n) for n = 1..1000
• Alexandru Gica and Laurențiu Panaitopol, On Oblath's Problem, J. Integer Seq., Vol. 6 (2003), article 03.3.5, 12 pp.
• Index entries for linear recurrences with constant coefficients, signature (0,0,100).

Crossrefs

Cf. A235717, A018885.

Subsequence of A000290.

Formula

a(n) = 100*a(n-3) for n > 22. - Stefano Spezia, Dec 09 2023