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 A098646 #18 Sep 08 2022 08:45:15 %S A098646 3,2,12,8,48,32,192,128,768,512,3072,2048,12288,8192,49152,32768, %T A098646 196608,131072,786432,524288,3145728,2097152,12582912,8388608, %U A098646 50331648,33554432,201326592,134217728,805306368,536870912,3221225472,2147483648 %N A098646 Trace sequence of 3 X 3 Krawtchouk matrix. %C A098646 Let A=[1,1,1;2,0,-2;1,-1,1], the 3 X 3 Krawtchouk matrix. Then a(n)=trace(A^n). %H A098646 Vincenzo Librandi, <a href="/A098646/b098646.txt">Table of n, a(n) for n = 0..1000</a> %H A098646 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,4) %F A098646 G.f.: (3+2*x)/((1+2*x)*(1-2*x)). %F A098646 a(n) = (-2)^n+2*2^n. %F A098646 Recurrence: a(n) = 4a(n-2), a(0)=3, a(1)=2. - _Ralf Stephan_, Jul 17 2013 %F A098646 a(2n+1)=A081294(n+1). a(2n)=A002001(n+1). - _R. J. Mathar_, Nov 11 2013 %o A098646 (Magma) [(-2)^n+2*2^n: n in [0..45]]; // _Vincenzo Librandi_, Jun 11 2011 %Y A098646 Cf. A074535, A098647. %K A098646 easy,nonn %O A098646 0,1 %A A098646 _Paul Barry_, Sep 18 2004