%I #14 Jan 28 2024 20:57:03
%S 1,121,12321,1234321,123454321,12345654321,1234567654321,
%T 123456787654321,12345678987654321,1234567891022847726601,
%U 12345678910116040727447056,12345678910111210088193915136,1234567891011121368630088707263161,12345678910111213145200045239801398529
%N Smallest square beginning with concatenation of first n natural numbers.
%e a(3) = 12321 = 111^2.
%e a(10) = 1234567891022847726601 = 35136418301^2. [Corrected by _Sean A. Irvine_, Jan 28 2024]
%Y Cf. A007908.
%K base,easy,nonn
%O 1,2
%A _Amarnath Murthy_, Feb 20 2002
%E More terms from _Ralf Stephan_, Oct 12 2002
%E a(10) corrected and a(14) by _Sean A. Irvine_, Jan 28 2024