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A061433 Largest n-digit square. 9

%I

%S 9,81,961,9801,99856,998001,9998244,99980001,999950884,9999800001,

%T 99999515529,999998000001,9999995824729,99999980000001,

%U 999999961946176,9999999800000001,99999999989350756,999999998000000001

%N Largest n-digit square.

%C When (if ever) does this differ from A069659?

%C 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 a(n) = (ceiling(10^(n/2)) - 1)^2. - Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 30 2003

%e a(4) = 9801 = 99^2 has 4 digits while 100^2 = 10000 has 5 digits.

%p A061433 := n->(ceil(10^(n/2))-1)^2;

%t Table[Floor[Sqrt[10^n-1]]^2,{n,20}] (* _Harvey P. Dale_, Aug 21 2014 *)

%Y Cf. A061432.

%K nonn,base,easy

%O 1,1

%A _Amarnath Murthy_, May 03 2001

%E More terms from Larry Reeves (larryr(AT)acm.org), May 16 2001

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Last modified October 22 05:36 EDT 2021. Contains 348160 sequences. (Running on oeis4.)