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 A061361 #5 Mar 05 2015 12:23:19 %S A061361 4,6,17,604,9612,85848855,109457393440691436, %T A061361 16484027824615378535694780556419522, %U A061361 2537811713051483817817710620248313487995814710180147690293469081793581 %N A061361 a(1) = 4; a(n) = least number such that the concatenation a(n)a(n-1)...a(2)a(1) is a square. %e A061361 a(3)a(2)a(1) = 1764 = 42^2, a(4)a(3)a(2)a(1) = 6041764 = 2458^2, a(5)a(4)a(3)a(2)a(1) = 8584885596126041764 = 2929997542^2. %Y A061361 Cf. A050636, A050637, A061359, A061363. %K A061361 nonn,base %O A061361 1,1 %A A061361 _Amarnath Murthy_, Apr 28 2001 %E A061361 Corrected by Larry Reeves (larryr(AT)acm.org), May 07 2001 %E A061361 More terms from Ulrich Schimke (ulrschimke(AT)aol.com), Nov 06 2001