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 A247387 #18 Sep 08 2022 08:46:09
%S A247387 21,42,21,42,14,8,7,21,42,21,42,14,8,7,21,42,21,42,14,8,7,21,42,21,42,
%T A247387 14,8,7,21,42,21,42,14,8,7,21,42,21,42,14,8,7,21,42,21,42,14,8,7,21,
%U A247387 42,21,42,14,8,7,21,42,21,42,14,8,7,21,42,21,42,14,8,7
%N A247387 Base-n state complexity of partitioned deterministic finite automaton (PDFA) for the periodic sequence (1234567)*.
%H A247387 Klaus Sutner and Sam Tetruashvili, <a href="http://www.cs.cmu.edu/~sutner/papers/auto-seq.pdf ">Inferring automatic sequences</a> (see table on the p. 5).
%H A247387 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,1).
%F A247387 G.f.: x^2*(21 + 42*x + 21*x^2 + 42*x^3 + 14*x^4 + 8*x^5 + 7*x^6)/(1-x^7).
%t A247387 CoefficientList[Series[(21 + 42 x + 21 x^2 + 42 x^3 + 14 x^4 + 8 x^5 + 7 x^6)/(1 - x^7), {x, 0, 40}], x]
%o A247387 (Magma) &cat[[21, 42, 21, 42, 14, 8,7]: n in [0..30]];
%Y A247387 Cf. A176059, A217515, A217516, A217517, A217518.
%K A247387 nonn,easy
%O A247387 2,1
%A A247387 _Vincenzo Librandi_, Sep 16 2014