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 A249910 #27 Jul 25 2016 09:42:26
%S A249910 2,4,5,7,5,4,2,4,5,7,5,4,2,4,5,7,5,4,2,4,5,7,5,4,2,4,5,7,5,4,2,4,5,7,
%T A249910 5,4,2,4,5,7,5,4,2,4,5,7,5,4,2,4,5,7,5,4,2,4,5,7,5,4,2,4,5,7,5,4,2,4,
%U A249910 5,7,5,4,2,4,5,7,5,4,2,4,5,7,5,4,2,4,5,7,5,4,2,4,5,7,5,4,2,4,5,7,5,4
%N A249910 Digital root of A003500(n).
%C A249910 Periodic with cycle of length 6: {2,4,5,7,5,4}. a(n) may be expressed as the decimal expansion of 246/1001. Sequence is palindromic.
%H A249910 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1, 0, -1, 1).
%F A249910 a(n) = 4*a(n-1) - a(n-2), reduced to digital root.
%F A249910 a(n) = digital root of (2 + sqrt(3))^n + ( 2 - sqrt(3))^n.
%t A249910 LinearRecurrence[{1, 0, -1, 1}, {2, 4, 5, 7}, 102] (* _Ray Chandler_, Jul 25 2016*)
%Y A249910 Cf. A010888, A003500.
%K A249910 nonn,base
%O A249910 0,1
%A A249910 _Peter M. Chema_, Dec 17 2014
%E A249910 More terms from _Ray Chandler_, Jul 25 2016