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 A216871 #32 Sep 08 2022 08:46:03
%S A216871 -4,4,-4,20,28,68,92,148,188,260,316,404,476,580,668,788,892,1028,
%T A216871 1148,1300,1436,1604,1756,1940,2108,2308,2492,2708,2908,3140,3356,
%U A216871 3604,3836,4100,4348,4628,4892,5188,5468,5780,6076,6404,6716,7060,7388,7748,8092
%N A216871 16k^2-16k-4 interleaved with 16k^2+4 for k>=0.
%C A216871 The sequence (the third in the family) is present as a family of single interleaved sequence of which are separated or factored out of the larger sequence to give individual sequences. The larger sequence produces four smaller interleaved sequences where one of them has the formula above and a second interleaved sequences having the formulas (16n^2-24n+1) and (16n^2-6n+5). This interleaved sequence is A214393. The fourth interleaved sequence in the group has the formulas (16n^2-8n-7) and (16n^2+2n+5) and it is A214405. There are a total of four sequences in this family.
%H A216871 Eddie Gutierrez <a href="http://www.oddwheel.com/square_sequencesIII.html">New Interleaved Sequences Part C</a> on oddwheel.com, Section B1 Line No. 23 (square_sequencesIII.html) Part C
%H A216871 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-2,1).
%F A216871 Contribution from _Bruno Berselli_, Sep 27 2012: (Start)
%F A216871 G.f.: -4*(1-3*x+3*x^2-5*x^3)/((1+x)*(1-x)^3).
%F A216871 a(n) = 2*(2*n*(n-2)-3*(-1)^n+1).
%F A216871 a(n) = 4*A214345(n-3) with A214345(-3)=-1, A214345(-2)=1, A214345(-1)=-1. (End)
%t A216871 Flatten[Table[{16 n^2 - 16 n - 4, 16 n^2 + 4}, {n, 0, 23}]] (* _Bruno Berselli_, Sep 26 2012 *)
%t A216871 LinearRecurrence[{2,0,-2,1},{-4,4,-4,20},50] (* _Harvey P. Dale_, Dec 09 2015 *)
%o A216871 (Magma) &cat[[16*k^2-16*k-4, 16*k^2+4]: k in [0..23]]; // _Bruno Berselli_, Sep 27 2012
%o A216871 (PARI) vector(47, n, k=(n-1)\2; if(n%2, 16*k^2-16*k-4, 16*k^2+4)) \\ _Bruno Berselli_, Sep 28 2012
%Y A216871 Cf. A178218, A214345, A214393, A214405, A216876.
%K A216871 sign,easy
%O A216871 0,1
%A A216871 _Eddie Gutierrez_, Sep 18 2012
%E A216871 Definition rewritten by _Bruno Berselli_, Oct 25 2012