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%I #7 Jan 20 2017 19:56:12
%S 1,6,9,744,41796,60172924176,8240010144800000000001,
%T 82400101448000000000020000000000000000000001
%N a(1) = 1; a(n) = smallest number such that the concatenation a(1)a(2)...a(n) is a square.
%C The next term is too large to include.
%C a(n) is at most doubly exponential in n. Is there also a double exponential lower bound? - _Charles R Greathouse IV_, Sep 19 2012
%H A. Murthy, <a href="http://www.gallup.unm.edu/~smarandache/SN/ScArt5/ExploringNewIdeas.pdf">Exploring some new ideas on Smarandache type sets, functions and sequences</a>, Smarandache Notions Journal Vol. 11 N. 1-2-3 Spring 2000.
%e a(1) = 1, a(1)a(2) = 16 = 4^2, a(1)a(2)a(3) = 169 = 13^2, 169744 = 412^2.
%Y Cf. A061109, A051671. The actual squares are in A048557.
%K base,nonn
%O 1,2
%A _Amarnath Murthy_, Apr 20 2001
%E More terms from Larry Reeves (larryr(AT)acm.org), Jul 23 2001