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A034980 a(n)^2 is smallest positive square starting with a string of n 2's.

%I A034980 #11 May 31 2023 14:54:58
%S A034980 1,5,15,149,4714,47141,471405,1490712,1490712,471404521,1490711985,
%T A034980 1490711985,1490711985,1490711985,47140452079103,149071198499986,
%U A034980 149071198499986,14907119849998598,14907119849998598,471404520791031683,14907119849998597976,471404520791031682934,4714045207910316829339
%N A034980 a(n)^2 is smallest positive square starting with a string of n 2's.
%H A034980 Robert Israel, <a href="/A034980/b034980.txt">Table of n, a(n) for n = 0..996</a>
%e A034980 a(5)^2 = 47141^2 = {22222}73881.
%p A034980 f:= proc(n) local x, k, s;
%p A034980   x:= 2*(10^n-1)/9;
%p A034980   for k from 0 do
%p A034980     s:= ceil(sqrt(10^k*x));
%p A034980     if s^2 < (x+1)*10^k then return s fi
%p A034980   od
%p A034980 end proc:
%p A034980 f(0):= 1:
%p A034980 map(f, [$0..30]); # _Robert Israel_, May 31 2023
%Y A034980 Cf. A034981.
%K A034980 nonn,base
%O A034980 0,2
%A A034980 _Patrick De Geest_, Nov 15 1998
%E A034980 More terms from Francisco Salinas (franciscodesalinas(AT)hotmail.com), Dec 23 2001