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 A082209 #30 Dec 14 2023 05:11:26
%S A082209 1,6,4,9,61,504,1,6,4,9,61,504,1,6,4,9,61,504,1,6,4,9,61,504,1,6,4,9,
%T A082209 61,504,1,6,4,9,61,504,1,6,4,9,61,504,1,6,4,9,61,504,1,6,4,9,61,504,1,
%U A082209 6,4,9,61,504,1,6,4,9,61,504,1,6,4,9,61,504,1,6,4,9,61,504,1,6,4,9,61
%N A082209 a(1) = 1, a(n) = smallest number such that the concatenation of a(n-1) and a(n) is a square.
%H A082209 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 1).
%F A082209 Periodic with period 6. - Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 20 2003
%e A082209 a(4) = 9 hence a(5) = 61 and 961 = 31^2.
%t A082209 PadRight[{},120,{1,6,4,9,61,504}] (* _Harvey P. Dale_, May 04 2013 *)
%t A082209 LinearRecurrence[{0, 0, 0, 0, 0, 1},{1, 6, 4, 9, 61, 504},83] (* _Ray Chandler_, Aug 26 2015 *)
%t A082209 CoefficientList[ Series[ (504x^5 + 61x^4 + 9x^3 + 4x^2 + 6x + 1)/(1 - x^6), {x, 0, 83}], x] (* _Robert G. Wilson v_, Nov 22 2015 *)
%o A082209 (Magma) &cat [[1,6,4,9,61,504]: n in [0..20]]; // _Vincenzo Librandi_, Nov 23 2015
%o A082209 (PARI) A082209(n)=[1, 6, 4, 9, 61, 504][(n-1)%6+1] \\ _M. F. Hasler_, Nov 24 2015
%Y A082209 Cf. A082210.
%Y A082209 See A090566 for another version.
%K A082209 base,nonn
%O A082209 1,2
%A A082209 _Amarnath Murthy_, Apr 10 2003
%E A082209 Corrected and extended by Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 20 2003