This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A061433 #12 Feb 20 2023 14:54:55
%S A061433 9,81,961,9801,99856,998001,9998244,99980001,999950884,9999800001,
%T A061433 99999515529,999998000001,9999995824729,99999980000001,
%U A061433 999999961946176,9999999800000001,99999999989350756,999999998000000001
%N A061433 Largest n-digit square.
%C A061433 When (if ever) does this differ from A069659?
%C A061433 Trivially, 81 is both a square and a fourth power. Assuming my program works, there are no differences in the first 1500 terms. - _Hans Havermann_, Aug 06 2006
%F A061433 a(n) = (ceiling(10^(n/2)) - 1)^2. - Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 30 2003
%e A061433 a(4) = 9801 = 99^2 has 4 digits while 100^2 = 10000 has 5 digits.
%p A061433 A061433 := n->(ceil(10^(n/2))-1)^2;
%t A061433 Table[Floor[Sqrt[10^n-1]]^2,{n,20}] (* _Harvey P. Dale_, Aug 21 2014 *)
%o A061433 (Python)
%o A061433 from math import isqrt
%o A061433 def A061433(n): return isqrt(10**n-1)**2 # _Chai Wah Wu_, Feb 20 2023
%Y A061433 Cf. A061432.
%K A061433 nonn,base,easy
%O A061433 1,1
%A A061433 _Amarnath Murthy_, May 03 2001
%E A061433 More terms from Larry Reeves (larryr(AT)acm.org), May 16 2001